AMA | July 2024

0:00:01.0 Sean Carroll: Hello, everyone. Welcome to the July 2024 Ask Me Anything edition of the Mindscape podcast. I'm your host, Sean Carroll. So, hot enough for you? I don't know where you are, or I don't even know when you're listening to this. But here in July 2024 in the United States of America, it's been hot outside. We've been getting dueling heat domes over different parts of the country, pushing temperatures pretty high. In Baltimore, in recent days, it's been mid to high 90s pretty regularly and will be in the rest of the week. And this is depressing to me, not just because it's hot outside. Okay, sometimes it's hot outside. But you know, it is our fault in some very legitimate sense that this is happening. We have brought this on ourselves. Not the fact that it's 95 today. Of course, there's a difference between weather and climate, as you all know. But the fact that there are more days like this than there used to be, the fact that the average is higher, the fact that the extremes are more extreme, is our fault, right? We human beings have done this. And I know that lots of people have resisted believing this. You know, as a physicist, I can point to physics colleagues of mine who twisted their brains into knots trying to convince themselves that, oh, it's so complicated, we don't really know. There's just so much incentive to not believe these things. It's an interesting test case.

0:01:26.7 SC: Forget about the atmospheric science of it, which is very interesting. But the psychology of it is very interesting. And I'm mentioning this because it will come up in this AMA. As we go, there's, people are a little frustrated. I'm getting questions along the lines of, are we doomed? What can we do? You know, things seem bad. And I have no easy answers for any of these questions. But the fact that we are doing it to ourselves is what kind of fascinates me. Not just with the climate, obviously. Politics is another area where this is happening. I'll give you just one example. Donald Trump, who is currently leading to be the winner of the presidential election this November, his major economic proposal is a tariff on all imported goods in the United States of 10%. Not just, the ones he thinks are non-competitive or whatever, the whole thing. And he's going to do this at the same time of cutting taxes to wealthy people. And this is going to be a disaster if it actually happens. I mean, who knows if it actually happens, right? But a tariff is a broad-based, comprehensive sort of take-no-prisoners tariff like that. No real economist thinks this is a good idea. You run the numbers. It's basically, it's going to make inflation skyrocket.

0:02:49.9 SC: And it will effectively amount to a tax of over $1,000 per US household per year. And if you at the same time cut taxes even further for wealthy people, you're just shifting the overall tax burden to poorer people, many of whom are going to vote for Donald Trump. And so this is this classic question about why people are acting in ways that are not in their apparent self-interest, whether it's the climate change or economic policy or whatever. And, maybe you would like to say, well, people aren't educated enough, right? Like, they're just low information. They don't know what they're doing, etc. It brings to mind, there's a screenshot of a tweet that has been passed around in my circles on Bluesky in recent days. It is a comment from Dan Shafer, who I don't know personally, or I've never heard of before. But apparently, he's a journalist, I guess, in Wisconsin. And so he writes, going through my notes from the Biden rally in Madison, Democrats so badly want to be talking about Trump and the policy contrast between the two parties. Every speaker hit on it over and over, and there's so much there. But it's clearly not the story right now. And it can't be. So someone asks, why can't it be? And Dan Shafer's reply is because much of the Trump criticism is nothing new. And what's happening with Biden is a bigger story, because there needs to be someone capable of defeating Trump. And right now, that's an open question.

0:04:23.0 SC: So look, I have no objection to people reporting and talking about Joe Biden's age problems. That's a perfectly legit thing to talk about. But the idea that we shouldn't talk about the actual policy differences between the candidates, the fact that we don't talk about the fact that Trump's economic policies would dramatically disadvantage many of his supporters, you can't completely blame supporters for this. Dan Shafer, I presume, is an educated guy. He's not a low information voter. He's a reporter who goes to political rallies, right? He thinks about the policies. He knows what's going on in this world. He just doesn't think that's what matters, the actual policies that the presidential candidates would enact. So this is why I said a few minutes ago, I don't have any easy answers to these questions about the doom and gloom that we're currently faced with. It's complicated. That's obviously a theme of my AMAs. We have to think about it in complicated ways. You can't just start at the end and say, "Well, I don't like this outcome. Let's pass a law prohibiting that outcome from happening." You have to start way back in the psychology of people, in their motivations, in the information they have, in the media ecosystem that they're in, how we vote for people, how we elect our representatives, the incentives there, the money that goes through, the advertising, a whole bunch of things.

0:05:50.8 SC: It's a comprehensive kind of thing. And I want to end this overly long intro, sorry about the overly long intro here, with even though I don't have a simple nostrum that will fix all these things, and even though I completely sympathize with the feelings of doom and gloom that people can get. Both of those are true, and yet you can't stop fighting. That's the real lesson. Go back to Hannah Ritchie's podcast that we did recently. She tried very hard to walk on this fine line between saying, "Yes, we're doing terrible things to the environment, but no, it's not hopeless. It might not be hopeless, but only if we do something, we actually take action." So I want to, we have to acknowledge the bad stuff that is going on in the world right now, and we can't stop fighting against the bad stuff, thinking about it, taking action in whatever way, large and small. Don't get depressed if the one little thing you do is not going to fix all the problems of the world. We have to keep doing things, we have to keep pushing in the right direction, and there's plenty of reason to believe that we can actually make the world a little bit less doomy and gloomy than it seems right now if we put our minds to it. So with that, let's go. Alex asks a priority question.

0:07:25.4 SC: I should have said this during the intro, but questions for the AMAs, for those of you who don't know, are asked by Patreon supporters of Mindscape, so you can be a Patreon supporter if you're not already. You can go to patreon.com/seanmcarroll and sign up, and then you get to ask questions, as well as getting ad-free versions of the podcast and other more intangible benefits. Sadly, even though there's not that many Patreon supporters compared to overall listenership, it's still way more than I can answer all the questions of. So I have to pick usually, and to make sure that everyone gets a chance to ask their most important question, we have the priority question system. Once per your lifetime, you're able to label a question as a priority question, and I will do my best to answer it. So Alex says, my understanding of Hubble tension is that there is a discrepancy between values of the Hubble constant measured two different ways, one using the cosmic background radiation, and second using objects that are much closer to us.

0:08:24.1 SC: In other words, they measure H-naught as it was 300,000 years after the Big Bang, and as it was much later. My question is, are lambda and Hubble constants related in such a way that recent results of the DESI project, D-E-S-I, Dark Energy Spectroscopic Instrument, which seemed to indicate that lambda is decreasing, can that help explain the Hubble tension? So short answer is, I don't think it does. I don't think it does explain the Hubble tension. That would be an easy kind of solution.

0:08:54.0 SC: So let me just clear up a little bit. You're right that the Hubble tension, as we talked about with Adam Riess on the podcast a couple years ago, is a discrepancy between two different ways of measuring the Hubble constant. The Hubble constant being the value of the expansion rate today. The Hubble parameter, which says what the value of the expansion rate is at different moments of cosmic history, of course changes with time. The Hubble constant, a little bit misnamed, is just what the value of today. And the two different measures are indeed one locally with galaxies moving away from us, usually through supernovae supernova or Cepheids or things like that. And then the other one is using the cosmic background radiation, which is a snapshot of what the universe looked like about 300,000 years after the Big Bang. However, when you use the cosmic background radiation to measure the Hubble constant, it is not that you are measuring it at 300,000 years after the Big Bang. Rather, you're using the model that we use to understand the universe, the so-called Lambda-CDM model. Lambda for the cosmological constant, CDM for cold dark matter. And there's more to Lambda-CDM than just the cosmological constant and cold dark matter. There's also an idea that the universe is expanding and cooling off and has density fluctuations with a certain spectrum and so forth.

0:10:12.5 SC: There's a whole bunch of ingredients that go into this model. And then there are free parameters in the model. So what is the density of matter? What is the density of the cosmological constant? What is the expansion rate? What is the amplitude of the fluctuations? All these different things. How many neutrinos do you have contributing to the energy density and so forth? And what you do with the cosmic microwave background is that you fit what you see in the anisotropies of the cosmic microwave background to the model as a whole, including all those different parameters that I just mentioned, one of which is the Hubble constant today. Okay. So you're using data from far away from the cosmic microwave background to measure the Hubble constant today in a very indirect way by fitting to all the predictions of this model for the anisotropies in the CMB. So it's not, of course, if you measure the actual value of the Hubble parameter at the moment of recombination when the cosmic microwave background was produced, it would be much bigger than it is today. That's not a surprise at all. Okay. But having said that, is it possible... So I should also mention that there were these results that were put out by the DESI project, D-E-S-I, saying that maybe there's a tiny bit of evidence that the dark energy, which is about 70% of the energy density of the universe, is not quite constant density in time, but might be slowly decreasing.

0:11:44.5 SC: As you may have heard, there's dark energy in the universe, 70% of it. The simplest idea for what that dark energy could be is the cosmological constant, Einstein's idea of a truly constant energy density. But we don't know. That's a simple idea. It's the one that I would put the most credence on. But it's absolutely possible that dark energy is slowly changing with time, and maybe the DESI project has seen the first evidence for that. Okay. Number one, I don't think that our evidence from DESI or anywhere else is very strong for that right now. Okay. So it might be true. It's absolutely something to keep an eye open for, but it'll take time for us to figure out whether or not that's correct or not. But the other more important thing is I'm not an expert on the actual ways to solve the Hubble tension. I do think that probably it will go away. That's still my first guess, but I am very, very open to it not going away. We'll have to wait and see. We have to be able to wait and see, right? That has to be our attitude as scientists. What I do know is if you could just solve it by saying that the dark energy was not precisely constant over time, people would have said that a long time ago. That's the very first thing that you check, and that doesn't work. That does not solve the tension.

0:13:02.0 SC: It does not resolve the differences in measurement from early times and late times. And that's one of the biggest reasons why I think that the Hubble constant tension probably will go away, not because the observers aren't good. The observers are incredibly good, and they're also incredibly careful. They're looking very, very hard for reasons why this tension might be there, and they haven't found any yet. But theorists are then going to say, "Okay, if it's real, how could we explain it?" And there's sort of explanations that make sense and are simple and easy, and explanations that seem contrived, right? So far, none of the explanations that claims to fit has been simple and easy. They all seem very, very contrived. And so that's one of the reasons why the Hubble tension is a little weird. It's not like you see, it's not like the 1998 discovery that the universe was accelerating, where you saw some data you didn't expect, but then you instantly said, "Oh, we know what's going on. We have a theory that explains this right away." The Hubble tension is not like that. We don't have a good theory that explains it, and slightly varying dark energy is not a theory that explains it, unfortunately. Sorry.

0:14:17.1 SC: Kevin says, "Do you have any advice for attending academic conferences? Do you try to go to every talk, speak to as many people as possible, or just do what feels right or comfortable?" You know, not just for conferences, but for academia more generally, I think there's a tension there. Here's a tension, not just a Hubble tension, academic tension. One is you get into academia because you're in love with this intellectual life, with the pursuit of ideas and knowledge and understanding the universe better. Very, very broadly construed. I don't just mean cosmology. Let's count, you know, literature and economics just as well. But then the actual idea of living your life, having a career as an academic, you discover is hard, because there are many more people who want to do it than there are jobs for it. So you are inundated sorry, with pressures to get a job, right, to network, to not only just get a job, but get acknowledgement and recognition for your work. Even if you already have a job, you still want people to care about the work you do and things like that. So there's all these pressures that are separate from, or orthogonal to, or maybe even opposed to living the life of the mind and just trying to understand the universe better. So my first piece of advice is to not forget why you got into academia in the first place. Why are you at this conference? Is it just to get a job? Are you completely uninterested in the... And Kevin, you didn't say this.

0:15:44.9 SC: I'm not accusing you of this, but there are people who act as if the only purpose of going to a conference is to sort of network and get a job. The first piece of advice is keep in mind that there is a higher intellectual purpose here. So if that is your purpose, and by the way, getting a job is fine too, and it doesn't... Getting a job is not like an evil or a purpose that you can't acknowledge. If you get a job, then you can keep doing this academic thing for the rest of your life. That's a good thing. That's perfectly okay. But it's not the only thing, is the point. So do you want to go to every talk? Probably not. It depends on the conference. If it's a relatively small conference or one that is focused on just a small number of talks, maybe invited talks by big name plenary speakers, then certainly going to most of the talks makes perfect sense. Many bigger conferences have parallel sessions and many things going on at once, and it's impossible to go to all of the talks. But it's perfectly okay to say, "Look, remember, I'm here to learn more about the field that I'm in. I will go to the talks I think are going to be interesting." There are many famous examples of interesting talks that people didn't think were interesting because they didn't have good titles or whatever.

0:16:57.5 SC: So you never know, and you might try to see a couple of talks that maybe aren't immediately speaking to you, but you don't have to. You shouldn't feel any moral obligation to go to every talk. Do what is enriching your intellectual life the best. Likewise for speaking to as many people as possible. Why are you speaking to these people? Do you actually have questions about their work? In that case, it's very, very good to talk to them. That's why you're there. I mean, most actual reward of going to conferences does not come from going to the talks. It comes from speaking to the other people who are there. But if you just want to sort of meet them so they recognize your name so that maybe they give you a job someday, that's much less effective than you might think. Unless you have done some really good work, unless you have a really good result or insight or contribution that you can let them know about that they would legitimately be interested in, then fine. It's absolutely okay to let people know about that. So again, it's not about speaking to as many people as possible. It's about speaking to people in productive, valuable ways. And not just people who are big and powerful. Absolutely, you should take advantage of speaking to people who are at whatever your level is, or even below your level.

0:18:11.7 SC: People who are younger, people who need guidance themselves. Those people might someday be very important, and even if not, they might be interesting right now. Take advantage of going to conferences to be you're surrounded by a bunch of people who care about the same thing you do. That's a very unique position to be in. Claudio says, "To account for the expansion of the universe, Fred Hoyle's Steady State theory proposed that matter had to be created, but at very low rates. Steady State theory was promptly disproven. But is the kind of creation of matter that Hoyle envisioned permitted by current views of field theory?" Well, not exactly the way that he envisioned it. So for those of you who don't know, the Steady State theory was the idea that not only is the universe more or less constant, homogeneous in space, more or less the same amount of density, if you look over very large scales, but it was also constant in time. The same rough expansion rate and density of matter in the universe at every different moment in time. That instantly runs into a problem with the fact that the universe is expanding, because when the universe expands, it dilutes the density of matter and radiation. So Hoyle's idea was that there was a field that spontaneously created more matter and radiation, the C-field it was called. And so that enabled the total density of matter to remain constant, and therefore you could get a steady state.

0:19:36.5 SC: So roughly speaking, no. I mean, this sounds a little bit similar to the cosmological constant, right? The cosmological constant is constant energy density, indeed. But the thing is, it just sits there. It does not turn into ordinary matter and radiation. As far as I know, there are no good field theory models of this kind of C-field that Hoyle proposed. If you try to do it in a naive way, you instantly run into problems with instabilities, right? With creating infinite amount of matter very, very quickly. So number one, it's hard to make it work on a field theory basis. Number two, the cosmological data don't require it. So people have not put a lot of effort into trying to understand that. Kyle Kabasares, sorry Kyle, says, "How much did you know about computer programming before going to college? And what was the first language you learned?" So I went to college in 1984, if you can believe that. That was a certain number of years ago. We won't calculate how many it was. And I knew a little bit of computer programming. And the first language I learned was actually Fortran. I took, of course, one semester course in Fortran in high school. So I knew the basics of that. I even helped write some programs that the school district used to do some, I don't know, filing. I forget what it was.

0:20:57.1 SC: Because it wasn't very common, right? We didn't have personal computers when I was in high school. So you had to, like, log into a mainframe and you had to get access to the mainframe. And all that was true. So I did a little bit of programming. And then when I went as an undergraduate, then that was the personal computer revolution when people started to have personal computers. I certainly didn't have one. I couldn't afford a personal computer. But in the astronomy department at Villanova, we had a lot of IBM PCs. And the native language at that time on those PCs was BASIC. Remember BASIC? BASIC was supposed to be like a watered down version of Fortran. And there was a, for some reason, they made a thing called QuickBASIC, which is actually just as powerful as Fortran, but more BASIC-like. So we did a lot of programming.

0:21:44.6 SC: And again, you know, useful programming, programming that was used for data analysis and reduction and so forth in QuickBASIC when I was an undergraduate. And I then took courses and studied a little bit. I learned a little bit of assembly language, a little bit of C at the time. So all of this was before we had things like Python or Lisp or any of the various Java-related things that we have now. So it was very useful, of course. It helps train your mind into thinking about what it means to be a successful algorithm or even what it means to explicitly give instructions for something. And I did that a lot when I was an undergraduate, but I sort of died down as I became more of a pencil and paper theorist as I went into grad school. Scott says, "Last month you shared your procedure for making pizza in a cast iron skillet." I think it makes good pizza.

0:22:38.2 SC: Instead of smushing the dough into the pan, have you tried stretching it and twirling it above your head? I don't know if it makes the pizza taste any better, but it is a lot of fun when it works. So no, I have not tried that. Well, I have made sort of more regular thin crust pizza on a pizza stone, in the oven, et cetera. I got recently, we purchased a new outdoor grill. Maybe I should try that. I've heard people say that on a good high temperature grill outside, you can make good pizza. But the twirling it over the head that brings me back. When I was a kid, we used to go to the local pizza joint, Maruca's Pizza. I still remember. And they would do that. It was a big show, right? Flipping the pizzas. And it never even occurred to me to think that I would have the capability to do that. But we should rise to these challenges. We should try new things. Maybe you will inspire me, Scott. I will let you know if that actually happens. Don't hold your breath. But I'll let you know. Alan Lubel says, "In the immortality episode, I think you mentioned, you don't want to live forever. You'd only like to live 10,000 years because there's a lot you'd like to do. But after that long, you'd be bored.

0:23:49.3 SC: My question is, wouldn't you want to risk a couple of years of boredom for potentially another 10,000 years of new experiences and relationships, and then another two years of boredom for another 10,000 years of new experiences and repeat the cycle on and on, thereby living forever?" So technically speaking, I'm not quite sure what you have in mind. I don't know why you think that it's just two years of boredom before you start the cycle anew. But there's two things going on here. One is the crucially important fact that human beings are finite, okay? That we do not have the capacity for an infinite number of things to interest us or happen to us or be absorbed by us. Our brains are not infinitely big, right? I do think that we have much more capacity to do things and try things and learn things and be amused by the world for much longer than 100 years, but I don't think that it is infinitely long. So the number 10,000 is, of course, pulled out of a hat.

0:24:44.5 SC: It was because of this workshop that I went to at Santa Fe where we were talking about immortality, and most people said they wouldn't even want to live 10,000 years. And I certainly think I would like to live 10,000 years, but I don't know. It's very possible after a few hundred years I would be irredeemably bored, irretrievably bored. I don't know what the right word there is. But the point is, I do think that we have a finite capacity for continuing to be interested in the world. I don't know how finite it actually is.

0:25:15.9 SC: Robbie P. Says, "Advanced alien intelligence or the wisdom of God compared to that of human beings is often analogized to humans and ants or similar. We imagine that advanced intelligences, who may have had much more time to evolve, would be so advanced that we could not hope to comprehend their technology or ideas. Does this make sense? I would think that since we can reason, we could at least in principle bridge any gap. What do you think? Is there anything we couldn't learn in principle?" So I think I'm mostly on your side here. I think that there is sort of a threshold one passes where one learns the idea of abstract reasoning. There's all sorts of inefficiencies and irrationalities and biases that we have, but we could learn to overcome those given time. I think that we human beings have the basic capacity for rational, abstract, symbolic thought. Okay. And once you have that, I don't think that there's another layer. Maybe there is, but I don't know because I don't have the thought capacity to think of it.

0:26:18.0 SC: But my suspicion is there is not another layer of mode of thinking that would give you an entirely different kind of capacity such that people stuck back in the human level couldn't possibly understand what you're doing. So I think, of course, you can get better at thinking, but it's still the same kind of thinking. We individual human beings are nowhere near as good as we can be at thinking, but we will get better and better, hopefully, at basically the same kind of thinking that we do now.

0:26:47.7 SC: But I don't think that's the worry with a super advanced civilizations. Not even the worry, but the point being made is not that they will think in different ways than us. It's not really like humans and ants. That's not a very good analogy if you're trying to analogize the mode of thinking that people have. But the technology that they will have developed, that is un-foreseeably more advanced than what we have right now. Even if I think that the way human beings do their thinking is not going to fundamentally change, the results of that thinking might very, very, very fundamentally change, and those I cannot anticipate. So I do think that advanced alien civilizations will be wildly, wildly different than either what we are now or what we can imagine they could be. I cannot predict what they're going to be. They will think in the same way, but they will have achieved enormously more than we have so far. PT Millo, I'm not quite sure how to pronounce this, says, "This is a pedagogical question about time. I've often heard you provide intuition for why time and space seem so different by explaining that time, number one, is a location like space, but with a negative Pythagorean sign in relating proper time to space-time coordinates, and two, is a dimension like space, but for us has an arrow." That's correct. I would say both those things. So the question goes on. "This always seems to elide my biggest intuitive lacuna.

0:28:14.4 SC: So when I finally read From Eternity to Here, I was surprised to read in chapter seven what I'd come around to as the salient missing distinction. Time is the dimension so heavily constrained by the dynamical laws that we decide to label many more macroscopic items as the same thing, changing across time. While space is so relatively unconstrained by rules that we are happier to say that objects simply end and become something else. My question is, why isn't this front and center in your more recent explications? Is it less critical than I imagine? Or have I otherwise just misunderstood it entirely?" No, I think it's very, very critical. And so just so everyone understands what's going on, the point is that the fundamental laws of physics, mostly because there's only one dimension of time and there are several dimensions of space, because otherwise the fundamental laws kind of look similar, right? But the fundamental laws leave us with particles moving slower than the speed of light. And that's a slight, not an exaggeration, but it's a dramatic oversimplification, because of course, really, there's field theory and quantum mechanics going on. But you know, the particles that we have in the universe persist through time. They do not persist through space. If I have, as the example I often use, if you have a table, I can have a table here.

0:29:37.6 SC: I use this example because when I'm talking on the AMA, there's a table in front of me and I can look and go, look, here is the table and here one centimeter to the right of it, there is not the table, right? It's just air. There's a dramatic difference between here and there. There's not so dramatic a difference from the table at this moment to the table at this moment, right? One second later, the table is more or less the same. There's that continuity through time, and that is ultimately traceable to the laws of physics. Plus this fact that we live in a world where things go slower than the speed of light. The atoms making up the table persist through time in a way that they don't persist through space. So, I mean, as to why I pedagogically don't talk about that much, maybe I should. It doesn't occur to me as the, I mean, this might be my fault. Maybe I should just confess a flaw here. Physicists don't talk about this that much because they go right to the mathematics of the equations that are governing how fields and particles behave in the universe. And there, the things that we mentioned earlier, the arrow of time and the different sign in the metric time versus space, those are the things that show up. And this thing about the persistence of matter through time, more so than through space, is a consequence of those more fundamental things, and therefore we don't think about it as much.

0:31:04.7 SC: But your implication might be completely correct, that maybe I should talk about it more or maybe it is the more visceral thing. Maybe it is the thing that people need to hear when trying to understand the difference between space and time. Or maybe not. Maybe this is something that some people care about a lot and others don't. I would be interested in knowing more about that. Domino asks a CAT question. Domino says, "I just moved from a condo high in the sky downtown Chicago to a house in the burbs, and my boy isn't acclimating well. Toby Ziegler is the name of the cat from the west wing. Toby Ziegler is a COVID cat. We got him during lockdown, so he's not in the least socialized to loud sounds. Humans other than my wife and me, also all of nature, etcetera. Anything far and seeming sends him scurrying back under the nearest bed. TZ is eating and using the litter box, so it's not too bad.

0:32:00.2 SC: But I worry about his long term psyche. He's very athletic and loves to find the highest perch in whatever room he's in, but here he'll barely jump on the couch while exploring during the rare moments he emerges in the first place. My question is about getting an update as to how Ariel and Caliban have been acclimating from your move to Baltimore and you've occupied two spaces. Right? It's only been a few days, and my research says this is normal behavior, but I'm dealing with an N equals one problem. Since you have technically quadrupled the data points that I do, I'm curious how they're doing in general and how long it took before the kitties were back to normal."

0:32:31.6 SC: Yeah, I think this is a very common thing, especially with cats. You know, look, cats are much more high strung, usually, than dogs are. Dogs can be high strung if they're individuals. But as a species, cats are much more sensitive and much less adaptable to these things. And especially if you have a cat who's only a few years old and has always been in one environment, and then you move them to a different one, that's a dramatic adjustment. Second thing is, individual cats can be very different from each other. This is data that I have because I have Ariel and Caliban, who are brother and sister, who grew up in exactly the same environment and who reacted very differently to moving. They reacted very differently to the process of moving itself and then to the acclimation process. Once we were there. Caliban is the more robust kitty. He rolls with the punches. He deals with the world as the world comes to him. He was not that upset when we put him in the cat carrier to actually go. Ariel was very upset. Caliban did. I think I've said this before, he had a little oopsie because he threw up. He got car-sick on the taxi ride from our LA place to the airport. But we had anticipated that. So we had a junky old towel in there, in the cat carrier, and he threw up on that. And once we got to the airport, we just threw that towel away, and he was fine. And then once we were in the airport, once we were in the airplane, Caliban was fine. He was, like, looking around.

0:34:01.1 SC: He was trying to flirt with flight attendants. He wanted to make friends. He wanted to walk in the plane and say hi to people. We didn't let him do that, but that's what he wanted. Whereas Ariel was petrified. You have to take the cats out of the cat carrier when you go through security. And we had them both in little leashes and so forth. And Jennifer was holding Ariel, and it was a struggle. She wanted to run away, she wanted to bolt. And Caliban was fine. And when we were in the plane, Ariel was cowering in the back of her little cat carrier, and Caliban was looking around. And then once we get to our new place in Baltimore, it was the temporary apartment. Ariel didn't want to come out of the cat carrier then. And Caliban was instantly out exploring things like that. Six months later, we move again, and it was the same kind of thing. Ariel found a place to hide in the house, and then she mostly hid, whereas Caliban was out exploring. So the good news is, point number three, they do adapt. Even Ariel does, did adapt to the new situation. She found her own places. She realized that it was okay that she was in a bigger house now. She had more things to explore, and she's gone, more or less back to exactly where she was. But it took a while. It took months, not days. And so I would be very, very patient with this. Tell Toby that he's a good boy and everyone loves him, but don't push him to do things he doesn't want to do, and he'll discover it on his own.

0:35:29.5 SC: Because, as you say, the natural mode of being for a cat like that is to scamper around and climb on things. And he will, I think, return to that fourth and final point is you can actually get little drops that you either feed them or just rub on their fur that slightly balance their pheromones, that sort of make them have more self esteem, or if you have two cats, make them less likely to fight. Right? So you can look into that. They're not like, prescription things or anything like that. But look on pets.com or wherever, ways to make your cat calm down after a move. That's absolutely something you can do. But the big picture is, I wouldn't worry. This is something that Toby will adapt to, I'm pretty sure. Peter Cain says, "In a 2023 episode of Doctor Who, a spaceship has fallen through a wormhole and found itself in a starless void stated to be so far outside of our universe that it would take trillions of years for the edge of our expanding universe to reach them. While I know that wormholes are likely impossible in a practical sense, is there anything in theory that would prevent one end of a theoretical wormhole opening outside of our universe in this way?"

0:36:42.1 SC: Well, it's not really outside our universe, I presume, given that they said it would take trillions of years. Look, they're not being very careful scientists here when they're writing Doctor Who, right? They're inspired by some articles they read on the web or whatever, that's fine. But if you can imagine traveling from point A to point B without using the wormhole, that even in principle, then you're not in our separate universe. You're in our universe. There's subtleties here with the expansion of the universe and being outside our horizons, maybe that's impossible in principle. But we're talking about the wormhole here. So, look, wormholes probably don't exist. Big macroscopic traversable wormholes probably don't exist, but we don't know for sure. And therefore, once you say, okay, imagine a wormhole exists, you're kind of unconstrained, you're kind of pretty free. If a wormhole did exist, the simplest thing to imagine would be that it would instantly collapse, okay, and go away. So, clearly, you don't want that to happen. You want a, what is called a traversable wormhole, a wormhole that is being held up by some kind of weird exotic energy. And you can imagine that that's fine. And then you want to imagine moving the two ends of the wormhole, right? You think of a wormhole as a little tube with two ends connecting different parts of the regular universe.

0:38:00.2 SC: And those two ends, in principle, you could imagine moving them. For example, you could move them with a gravitational field. You could, like, just pull on the wormhole through the force of gravity, pull a little bit more on one side than the other, and separate the ends. Or you could throw some charged particles into the wormhole, and then from the perspective of an outside observer, it would look like one end of the wormhole was positively charged and one was negatively charged. And then you could manipulate those with electromagnetic fields, which are much more reliable and easier to control than gravitational fields.

0:38:33.4 SC: So, in principle, you could move the ends of the wormhole around. I don't know if anyone has a careful solution to Einstein's equation saying, what would happen if you tried to do that? But that's the rough intuition we have. And then once you imagine all those things, once you're granting yourself all of these hypothetical powers, there's no reason why one end of the wormhole couldn't be really, really, really far away from the other one. Now, of course, what you want is the distance as measured through the wormhole remains small. If you pulled the ends of the wormhole apart, but the distance that you travel when you go through the wormhole grows as you pull the ends apart. Then you're not doing much good, right? Then you're not really saving yourself any travel time. So you're imagining that, once again, you're helping yourself to the supposition that that length does not grow. But again, nothing in the known laws of physics prohibits any of that. So in that episode of Doctor Who, that is not the part of science that I would complain about, let's put it that way. William Bryan says, "From what I understand, a particle accelerator is a very complicated thing that is a tremendous feat of engineering and science, but that it requires such a herculean effort from us to make a particle collision.

0:39:48.0 SC: I wonder why we can draw so much from it. I don't imagine many people think that the Big Bang was created by a particle accelerator. Obviously, there's a ton of interesting and important information gleaned from them. But why do we think a collision created in a particle accelerator is analogous to what happens in nature?" This is actually a great question, and if I understand the question correctly, I mean, it's very, very close to a question I care about a lot, which I will rephrase the following way. When we talk about the standard model of particle physics or the core theory or anything that we know about fundamental particle physics, Quantum Field theory, etcetera, most of that knowledge at the detailed level comes from experiments that we do with relatively small numbers of particles at a time, right? Smashing two protons together, seeing what comes out. Even if millions of particles come out, that's still way less than Avogadro's number of particles, right? It's way less than any macroscopic system, much less the Big Bang. So if we derive from that microscopic equations, microscopic meaning, applying to things on arbitrarily small length scales. If we derive from those equations of motion for particles and fields and so forth, what right do we have to apply them in cases that are very different than just a small number of particles smashing into each other?

0:41:08.0 SC: The short answer, there's sort of two answers. One answer is Quantum Field Theory says so and this is a lesson that you will hopefully get. I don't specifically talk about this issue, I think, but the basic underlying idea is in quantum fields. The biggest ideas in the universe, volume two, when we talk about Effective Field theories. The idea of an Effective Field theory basically guarantees that if you try to modify the equation, equations of motion for fundamental particles in ways that become important when many, many particles are involved, then the rules of Effective Field theory, not the rules, but the intuition of Effective Field theory says, sure, you can do that. But the numbers associated with those changes are gonna be very, very, very, very small. Okay. The actual impact that we'll have on the dynamics of the particles and fields you care about is essentially negligible following the rules of Effective Field theory, so one answer to your question is if Quantum Field theory and Wilsonian Effective Field theory are right, you don't have to worry. The rules that we get on the small scales work. The other answer is empirically it works, right?

0:42:29.1 SC: We don't use the standard model of particle physics when we do psychology or even much material science, but we do sort of build things up, right? We have expectations from the standard model about how atoms work. We have expectations from atoms about how molecules work. We have expectations from molecules about how chemistry works and how cells work and all the way up. And we haven't seen any inconsistencies anywhere along the way. So our expectations are that everything that we know about the rules of particle physics should continue to be valid and all of our experience is consistent with that. If anyone comes up with a good theoretical reason or a good experimental prediction that violates that, then we're more than more power to them, but we don't have any such things that I know of right now. Eric Davigi says, "Do you Sean feel like the Mindscape community is a place to discuss some of the acute threats facing American and world humans and ecosystems? Or are you trying to keep this community focused on science and philosophy?"

0:43:29.2 SC: Well, I definitely don't think that I'm trying to keep it focused on science and philosophy. I'm trying to keep, not even trying to keep it focused on anything. My self conception of what Mindscape is about is about ideas, is about trying to understand the world better. You all know the famous quote from Karl Marx and he's in his theses on Feuerbach. So he was responding to the German philosophers that slash theologian Ludwig Feuerbach. And Marx says, "Philosophers have always tried to understand the world. The point, however, is to change it." And, whose point? It is a point to change the world. That is an important thing to try to do. But it is also important to understand the world. And I would argue that we're gonna be more effective at changing the world to make it better if we understand it better. So it's not that I am not interested in changing the world and making it a better place but I take my own personal abilities and interests to be closer to trying to understand the world. However, having said all that, I'm very much in favor, a very much supportive of the idea of keeping the world going. This idea that we sit around and think about physics and philosophy and so forth. I get that this is a luxury. This is something that we are afforded the ability to do 'cause our basic material needs are being taken care of our basic safety needs are being taken care of and so forth.

0:45:02.8 SC: We live in a world where we're allowed to talk about such things without the government arresting us, and so forth. And therefore, it is absolutely valid to care about keeping those nice things about the world nice and even making them nicer in whatever way we can. So those aspects will absolutely leak into Mindscape from time to time. And if in the discussion, comment sections on Patreon, or on the website, preposterous universe.com, if they wanna talk about those things in greater detail, there is a Reddit, a subreddit, Sean M. Carroll. That you can talk about episodes of Mindscape if you want. So there's plenty of places for people to talk about the things that get brought up here. And I'm all in favor of those discussions being as wide ranging as they would like to be. François Varchon says, "In your podcast with Chiara Mingarelli, she described the interior of a black hole as resembling a water fountain, with light coming out and being processed around the singularity.

0:46:03.8 SC: This poetic imagery is quite striking to me, and it leads me to wonder, what do you think the inside of a black hole's event horizon looks like? How would you describe the entire black hole event horizon using similar imagery?" Well the short answer is the inside of a black holes event horizon doesn't look that special. In fact, I would slightly dispute Chiara's analogy there. I mean, I get it, and it's illuminating in some ways, but I don't want you to push it too far beccause it it kind of goes hand in hand with the old fashioned incorrect idea that the singularity is a part of the center of the black hole. That's not true. There is a center of the black hole, but it's not where the singularity is. The singularity is a moment of time in the future, into which you will travel as you age when you're inside the event horizon.

0:46:54.5 SC: So it's not like you enter the black hole, and you suddenly see a singularity over there to your left or in front of you or anything like that. Mostly what you see is what you saw before you came into the black hole. Remember, the event horizon of a black hole is defined by the fact that light can travel into the black hole from the outside world, but it can't travel out. So when you're right on the event horizon, half of what you see is the interior of the black hole. The other half is the exterior of the black hole. You see light coming from both directions. Actually, that's quantitatively not right. When you're right on the event horizon, you don't really see the interior because you have to travel faster than the speed of light to get to you. When you're somewhat inside, there's sort of some angle that you're looking at that lets you look inside the black hole and then a different angle lets you look outside. If the black hole is very, very big, and there's not a lot of matter falling into it or whatever, then you still see empty space around you. All of this is, I've never sat down and gone through the details of this, but of course there are strong gravitational fields, there are gravitational lensing, so the way that you see light coming in from outside can be distorted by the gravitational field of the black hole.

0:48:06.1 SC: I've never sat down and thought about that, but the basic thing is that the event horizon is not a super special place. You don't notice it when you hit it locally, so don't expect a sign there saying, this is the point of no return, now you're in trouble. Peter Newell says, "In relativity, rather than thinking of a meter as a unit of length and a second as a unit of duration, can you think of both meters and seconds as units of space-time? And if so, is it correct that the speed of light converts between meters and seconds in the same way you might need to convert between miles and kilometers?" Yes, this is exactly right. That is the correct way of thinking about it. I don't have much more to say than that. Once Einstein and Minkowski showed us that space and time could be wedded together to make space-time, then of course you have to measure them using one kind of unit, and the point of the speed of light is it is precisely the conversion factor between ordinary units of distance and ordinary units of time. Jonathan Goodson says, "In the last AMA you said that when the Schrodinger wave collapses, information is lost? Why isn't that loss an unacceptable violation of unitarity?

0:49:17.6 SC: Why is the loss of information inside a black hole a problem, while loss from a wave collapse is not?" Well, physicists tend to be in denial about the collapse of the wave function. Yes, it is a loss of information, but we don't know exactly what happens, right? We don't agree on what happens when the wave function apparently collapses. That's the measurement problem of quantum mechanics. So in the way that we teach quantum mechanics in textbooks now, there are two different ways for wave functions to evolve. When they are not being measured, they obey the Schrodinger equation and information is conserved. When they are being measured, the wave function collapses and information is not conserved. Why is that acceptable? Because those are the rules. That's just what you're taught. That's what quantum mechanics says, according to the traditional textbook or Copenhagen way of thinking about it. The reason why black hole information loss becomes a bigger deal is not because people love information and don't want it to be lost, okay? It's 'cause the black hole is purportedly destroying information over and above the collapse of the wave function, okay?

0:50:30.8 SC: So physicists have learned to internalize the idea that measurement is an irreversible, non-unitary process, but when you're not measuring it, everything should be unitary, which means obeying the Schrodinger equation, conserving information. So the problem with black holes seem to be that even if you're not observing it, it's destroying information. Even though everything should be obeying the ordinary rules of quantum mechanics, what's going on there? And you need to be more sophisticated about it than that. You could say, "Well, maybe the information is going into the black hole and it's lost to us, but it's still maintained by the universe." So you have to be a little bit careful about saying, "Oh, okay, what about when the black hole completely disappears?" Then you've gone from a pre-black hole state to a post-black hole state, and apparently information was lost even though you didn't measure anything. That seems bad, right? And of course, if it were true that information were lost and there was the correct theory that showed that that happened, as Stephen Hawking and others have advocated, then you would learn to deal with it. But it's hard to make such a theory actually work.

0:51:36.5 SC: Now, having said that, I do think that it's problematic that physicists have not paid enough attention to what it means to do a measurement in quantum mechanics. And I think that in many worlds, there's nothing special about measurements. It's just that we don't see the whole wave function. There is no loss of information to the wave function of the universe ever in many worlds. That's one of the reasons to think it's a good theory of quantum mechanics. I'm gonna group two questions together. One is from Kyle Stevens, who says, "The recent Supreme Court ruling on presidential immunity has sparked an intense reaction amongst the American people. Many people are calling for Biden to fight fire with fire and exercise this newly granted immunity to prevent Trump from running for President Les Trump exercise it himself. Do you believe it is ever advisable to further erode democratic institutions in the name of preventing a worse evil from taking hold?"

0:52:30.0 SC: And then Reece Johns says, "I'm from Wales in the UK the Supreme Court ruling for Trump scares the crap out of me. Can only imagine what liberals in the US are feeling. What is your reaction? As an aside, as a lawyer over here? The system of allowing politicians to choose Supreme Court seats has always seemed anti-democratic and to confuse powers of pillars of state, which should always remain separate. Is this something you can see a good argument for changing or keeping?" So yeah, for those of you who don't know, or for people who are listening in the far future where we've all been uploaded into the matrix, we just had quite a week here in the United States full of Supreme Court decisions that are bad.

0:53:09.4 SC: The one that is most shocking to people and horrifying was with Donald Trump. I think it was literally Trump versus US, which is a very, it's a laden title for a Supreme Court case. Trump versus US, where he was claiming that because he was president, he was immune from prosecution for criminal acts performed while he was the president. And the argument for it was supposed to be that if you could prosecute people who had been president for their criminal acts, then every time the presidency changed office and a different political party was in charge, they would undergo these political prosecutions of their predecessors. Now, there's two problems with this. One is, there's many problems with this. Let's put it that way. One problem is, clearly, this is not what the Constitution says. Like it is very, very clear in the text of the Constitution, in the deliberations when the Constitution were written, whether you're an originalist or any other version of constitutional legal theorist, you can't actually justify the idea that the president is immune from prosecution for what the president does in office. That is nowhere to be found. In the Constitution of the United States, they just made it up. In terms of legal reasoning, it is pitifully bad.

0:54:31.2 SC: The second thing is, the effects of this are gonna be terrible. So they're balancing the Supreme Court, if you take them at face value as trying to do a good job here, they're balancing two worries. One worry is what we just said, which is that there will be political prosecutions of former presidents by their opponents once they're out of office. And that would have a chilling effect on what presidents can actually do while they're in office. The other thing that they're trying to balance is that presidents, if they think that they have immunity, will do bad things. Now, there are two things, sorry to keep subdividing here, but there are two things to keep in mind about this balancing between political prosecutions of former presidents versus presidents doing bad things 'cause they know they're immune from prosecution. One is, the latter has actually happened, right? The majority opinion in the Supreme Court case is what do you think is gonna happen? The president is gonna try to overthrow an election or something like that? This is a hysterical hypothetical that the minority is putting forward here. But we know that actually happened. It actually occurred. It is not a hypothetical. The prosecution of former presidents is entirely hypothetical because, and here's the really important fact here, it is true that Donald Trump is on trial for various criminal activities, but he clearly committed these crimes.

0:56:06.4 SC: The weird thing about this Supreme Court decision is it assumes or presumes that there is essentially no relationship between committing crimes and being prosecuted for committing crimes. It assumes that the idea of prosecuting people for crimes is entirely one that is just sort of whimsical and arbitrary, and therefore you're gonna do that to your political opponents. Now, even though Trump right now is being prosecuted, it's not by Joe Biden, it's by various, it's, different parts of the Department of Justice, which is a federal thing indeed, but Biden himself has not been pushing for these prosecutions. And then there are state prosecutions that have nothing to do with the federal government at all. That is the one that he's actually been found guilty of 34 felony counts, and that was a state trial.

0:56:56.9 SC: So this decision is gonna go down in history, like objectively looking at it. I know I'm not objective about this, but this is gonna go down if you're 100 years from now, if there's still a democracy in the United States and you're still studying the history of it, this is gonna be up there with the Dred Scott decision that said that, Black people are not citizens and things like that as one of the historically most terrible decisions there is. And it was a six to three vote where split along clear party lines just yet again, if anyone even temporarily thought that justices all the way up to the Supreme Court and judges throughout the judiciary were not political creatures, this would completely fly in the face of that. So what to do about it is the question. To Kyle's question, can you fight fire with fire by Joe Biden, preventing Trump from running for office?

0:57:54.5 SC: Well, no, I don't think that's a very good idea at all. Technically what Kyle says is, do you believe it is ever advisable to further aero democratic institutions in the name of preventing a worse evil from taking hold? Maybe it would be, this is one of the difficult things about the collapse of norms, the collapse of institutions, the collapse of democratic ideals more generally is that you sometimes have to do things you don't wanna do in order to fight against, in encroaching fascism right now. You have to stand up to it in some ways, but this particular way of having Joe Biden or whoever try to, prevent Donald Trump from running for president, that's not the way to do it, because you have to think longer term than that. You have to imagine, okay, what happens if you did to do that? What are we trying to restore if you, you can't bomb the village in order to save it. And I think that's what this would amount to in this case, what Reece is asking is about how you choose the Supreme Court in the first place.

0:58:53.7 SC: And I think this is something where there, what I would say is that the current process of choosing Supreme Court justices and keeping them etcetera, is terrible. It's just not very well designed. I give the people who wrote the Constitution of the United States enormous credit for building a system that lasted as long as it did, but of course, they didn't get everything right. And this particular system of choosing and maintaining Supreme Court justices is terrible. There's no reason why justices should have lifetime tenure. And I mean, that's part of the, there would be no problem in having, let's say there's an 18 year term, right? So there's nine justices that you get a new justice every two years that would be perfectly sensible. But what has happened, sort of not because of the legal code, but 'cause of the political standards of the day, is that the process of choosing the justices has become highly, highly politicized, right?

1:00:00.2 SC: You can't pinpoint the moment that that happened, but Barack Obama nominated Merrick Garland to be a Supreme Court justice. He was a very moderate choice, who Republicans would in principle be happy to support under ordinary circumstances, but they saw an opportunity to just delay and not vote on that particular nominee until the next president came in and it was Donald Trump. So, through political machinations, even though consistently year to year the popular vote for presidency has been mostly Democrats, we end up with a Supreme court that is six to three Republicans. And so that is a bad system, and I don't know how to fix it. I am not very much in favor of court packing or expanding the size of the court for the various obvious reason. Let's say Joe Biden says, "Okay, you we're gonna add 10 more Supreme Court justices," and he picks all Democrats, what's to stop the next Republican president from adding 100 more Supreme Court justices and add picking all Republicans?

1:01:09.2 SC: It's not a sustainable way to do it. You need a sensible system in there. As is often the case, it's impossible to get a sensible system because the people who are in power are benefiting from the bad system that we currently have. So I don't really know what to do about that, but I do think that if we imagine living in a world where we try to make a sensible system of government, the current way of choosing Supreme Court and the current way of letting them have these lifetime appointments is certainly not the right idea. Dan Butler says, "In your episode with David Deutsch, you two disagreed about Bayesian reasoning when applied to scientific theories, but the nature of the disagreement wasn't totally clear. So I wanted to press you a little bit more to really understand your position each time you do a GR calculation, general relativity and see it vindicated by experiment, does your credence for GR increase?

1:01:55.7 SC: If so, your credence would approach one exponentially quickly, yet it is totally plausible that a deeper theory than GR will be found tomorrow, irrespective of how many confirming experiments have been done to date. How do you think about this?" Yeah, I think about the using Bayes theorem. I'm 100% a Bayesian on this case. So yes, every time you do a GR calculation and see it vindicated by experiment, your credence for GR will increase. But it's not quite that simple, right? You actually have to be, this is what the good thing about being a a Bayesian is that there's a formula, there's bases formula, and you don't just say, "Oh, there's general relativity degrees with the data." You compare it with the alternatives, okay? And your credence goes up. If general relativity predicts something that is compatible with the data and the alternatives predict something different that is not compatible with the data.

1:02:51.6 SC: If you have two theories that are predicting the same thing for your experiment, then your credences don't change when you do that experiment. And general relativity has been so well verified already that generally the kinds of theories that we are dealing with these days make the same predictions as general relativity for the vast majority of kinds of experiments that we do. So our theories are our credences for general relativity are not being driven so close to one that they can never change, right? That's just good Bayesian practice, especially when, if you're being consistent and careful about updating your credences, you take into account two things. Number one, your experiments are never perfect, okay? So there's always gonna be some errors there. And number two, you don't fully understand the space of alternatives, right? Some of your credence has to be sitting on a theory I haven't thought of yet.

1:03:34.8 SC: So that credence should never go very close to zero because you're not that smart. And so good Bayesian will absolutely put some credence on that, and that's completely compatible with, getting new evidence in that is also compatible with general relativity. And if I actually did do an experiment where I had a new theory of gravity that has agreed with general relativity on all the previous experiments, but disagreed with it on the new one, and the new one comes in and agrees with a new theory, then a good Bayesian is gonna say, 'Aha, now I should increase my credence with the new theory quite a bit and I will keep doing it. I won't do it right away. I will not switch." This is the difference. This is why I think that the Bayesian way of thinking about these things is better than the pap way 'cause there is no sort of, "Oh, I falsified it, I move on with my life." Rather, you say, "Well, I've increased my credence '

1:04:30.2 SC: Because of this experiment. Let's keep doing more experiments and I'll try to increase my credences more and more." I think this is just rationality, honestly. Steve Gore says, "For a lot of the history of science, it was possible for individuals to be competent across the entire body of scientific knowledge, limited only by opportunity and ability. This gradually became less achievable as that body of knowledge increased in breadth and depth, especially in fast moving highly technical sciences such as physics.

1:04:58.3 SC: As the sheer amount of physics knowledge increases, presumably the time investment needed to reach the cutting edge, even in increasingly narrow subfields continues to increase because getting to that edge involves exposure and understanding the previous work that is built on. Is it possible that the knowledge and experience new physicists need to be capable of making advancements will increase to the point of being effectively impossible to acquire over realistic working lives?" No, I don't think that that's really, I mean, it's possible, as I generally think that things are possible, but it's not a plausible thing to worry about. I think that the right way to say it is that this increase in knowledge leads to hyper-specialization, and therefore people become less and less familiar with adjacent fields in addition to their others.

1:05:42.9 SC: That's definitely a worry, and that's a reason to make it easier for people to talk to each other. But the thing about the advance of science in any one field is that you don't have to remember everything that came before you, right? You do not have to be an expert in Phlogistian theory or, you don't even need to be an expert in ether theories or something like that to be a modern general relativist, right? The nice thing about physics is it encapsulates its theoretical knowledge in relatively compact forms.

1:06:15.7 SC: So even though, Quantum Field theory is a lot, it's still a finite amount of things that you need to know. So I don't think there's any, at least not in my lifetime or yours, there's any worry that physics will become so advanced that no one human being can understand it well enough to make advancements. Dragon Sighted says, "In episode 280, Francois Chollet pointed out that LLMs only interpolate between points in vector space. But the genetic algorithms can find entirely novel points. When a human artist makes new art, they're influenced by all the art and culture they've absorbed, and they throw their personal unique spin on it. Suppose someone trains an LLM on human art and incorporates a genetic algorithm, smart randomizing component in the generation process, do you think the resulting program could be usefully labeled creative?" I think that's gonna depend on details of how the program works, but I think that I would agree with Francois that in principle, yes, I don't see anything, in principle that prevents algorithms from being creative.

1:07:18.1 SC: The point about that, both Francois and I make about AI is that there's a certain approach to AI that is encapsulated by these modern large language models. It's not the only approach and it has certain limitations and it has certain strengths. It is not general intelligence, but it still could be very useful. And that's not to say that we can't achieve creativity and general intelligence by other ways. That's why Francois is leading this, or at least, pioneering and promoting this, kind of intelligence test that really is trying to capture something closer to intelligence rather than just memorization. And the LLMs tend to not do that well on this test because they're good at memorizing, they're less good at imagination or creativity or true intelligence. Chris A says "In your, the biggest ideas in the universe books, you talk at various times about physicists solving the Einstein equation and solving the Schrodinger equation for different systems.

1:08:15.1 SC: What do the solutions look like? I know the solution for a quadratic equation looks but I have no intuition for what the solution to an Einstein or a Schrodinger equation is, or its physical meaning." This is a great question, and I think from various comments that I've received along these lines that I probably goofed here, or at least I didn't do as good a job as I could have in these books with the idea of solving equations. Because as someone who's been this for a long time, I know what it means to kind of take it for granted that people know what it means. Yeah, I make a big deal in the books about saying, "We're not gonna concentrate on the process of solving the equations, but people have solved the equations. Here's what the solutions look," etcetera, without really catching our breath and saying, "What does it mean to say I have solved an equation?"

1:09:02.7 SC: And I think for this particular question, the distinction you have in mind, if Chris says, "I understand what it means to solve the quadratic equation. So ax2+bx+C=0, what you're looking for are values of x that plug in and can solve that equation. The difference is the important difference I think that what you're getting at is when you look at Einstein's equation or the Schrodinger equation, these are differential equations, not algebraic equations. What that means is the quadratic equation is an algebraic equation. It's just multiplying things together, adding them together. A differential equation uses calculus that takes derivatives, and therefore the kind of thing that will be a solution to a differential equation is not a number. Numbers, values of variables are things that solve algebraic equations. The things that solve differential equations are functions.

1:10:01.4 SC: That is to say not just x=3, but f of x for all possible values of x, f of x=sin x or x squared or whatever. So for example, if I have a differential equation which says the derivative of x is equal to x, sorry, that's exactly wrong. I shouldn't say that. I have a function f of x, and I have a differential equation that says the derivative of f of x is equal to f of x. Okay, then I'm gonna have a function f of x that solves that. In that particular example, the solution would be f of x equals e to the x for Einstein's equation, the solution will be a metric tensor. That is a function of all the coordinates of space time for the Schrodinger equation. Likewise, the function that you're solving for is the wave function function. It'll be a function of space and time.

1:10:51.2 SC: That's what you're looking for. George Hampton says, "Since you are relatively well traveled, if you had to pick a different country to live in, where would you live? In addition to considering all the things one normally would also specifically think about the country's government and its ability to have and maintain a small l liberal democracy." Honestly, I don't know. I think it's a perfectly valid question. But I have not done anything systematic by way of investigating other countries to live in because I have no plans to live in other countries. I think there's plenty of countries that are very livable. Playing this game of thinking about the future of the government, though is a tricky one, right? As I'm recording this, we just had two elections in the UK and in France where the left side did much better than anticipated before the elections were actually held than the right side did.

1:11:44.3 SC: So that was a bit of a surprise. So if you're trying to predict the future on the basis of pundits, prognostications, that's hard to do. But also there is more to life than living in a comfortable government or environment. I grew up in the United States. I'm very well acquainted with the flaws of the United States, but my interest is in improving those flaws, right? I don't wanna just leave the United States to be somewhere else where it has a functioning democracy. I wanna preserve functioning democracy here in the country where I was born and raised. That's not some, that absolute prohibition against moving elsewhere. I've contemplated moving elsewhere. I've had job offers in other countries, taking it very seriously and would be happy to do so. But I would not, I'm just saying I would not leave the United States because the government was backsliding on the promise of democracy.

1:12:38.9 SC: I would fight to prevent that from happening. That would not be enough to make me wanna move. Elliot Speck says, "I enjoyed listening to Christophe Domi talk about how information makes sense of biology, but I was befuddled by his comment that complexity is literally just information. Whether I'm looking at the evolution of the cosmos or stirring cream into my coffee, both the initial high information state and the final low information state are low in complexity. It's the intermediate state that is complex. What am I missing?" I don't think you'll be surprised when I tell you that what you're missing is that people define the words complexity and information differently from time to time. And, Christophe is a wonderful scientist, and that's a great book that we talked about. But he has his very specific views on what these words should mean. I try to be more pluralistic about these things.

1:13:30.1 SC: And words can mean different things depending on the context. As long as you're clear about what you're saying. I think that one of Christophe's mottoes is that information is what can be measured or monitored by some apparatus. It's sort of relevant, functional information. So when I would say that the early universe is high information content 'cause it's low entropy, that's a different definition of information than what Christophe would would give because it is so simple back then. There's no part of the universe that gives you an extra amount of knowledge about the other part. Exactly when everything is uniform, giving me data about what's going on in one place in the universe tells me nothing new about what's going on in some other place 'cause I already knew, right? Everything is completely uniform. Once you know what's going on in one place, you know everything.

1:14:21.2 SC: Whereas once you have complexity, then I can have representations of what's going on one place in another place. I can have a book that has information about what's going on somewhere. I can have a photograph, I can have mutual information as it is called. So I think that's what he's getting at. But you shouldn't be worried about it. You should just keep your wits about you. When people use words like entropy, complexity, information, Larry Rossi says, "If you were in charge of assembling the elite committee that would rewrite the US Constitution for the modern era, but not rewriting it yourself, how would you decide who is on the committee?" Yeah, I love this question. This is entirely hypothetical because it's not gonna happen and I don't want it to happen. I do, I would love it if the US Constitution were rewritten by the right people, by the right process, with the right intentions.

1:15:15.6 SC: The chances that if we actually took up the challenge of rewriting the US Constitution at a constitutional convention, it would be done by the right people. Using the right process for the right reasons seem to be infinite, tiny. Therefore, just as a matter of caution, I would rather keep the Constitution as it is, frankly, try to amend it piece by piece rather than changing it wholesale. But let's say we're in a utopia, or let's say that I am the God emperor and I get to pick who rewrites the Constitution. Nothing that I'm gonna say is gonna surprise you. Let's put it that way. I would want smart people. I would want people who are experts, people who are both experts in the scholarly side of things, okay? So people who know the United States Constitution and its history forwards and backwards.

1:16:05.5 SC: People who are experts in constitutions throughout the world and throughout history. People who are experts in different forms of government, okay? Different ways that government has functioned, and in the dynamics of government, in the sort of complex systems side of things, how the choice of laws and constitution affects people's behavior and vice versa. I would also want some practical experience there. I would want some people there who were not ivory tower academics, but were politicians or judges or activists or whatever, who could speak to the interplay between the written words that you have in your constitution and the actual things that happen in the world. And finally, I would like diversity along many different, axes. I would want political diversity. I would want conservatives and liberals, as long as they were confined to people who believed in the idea of constitutional liberal democracy.

1:17:03.8 SC: I would want those kinds of people. But you can have people who want the tax code to be very light and to be very heavy, you want of all those kinds of people. I would want people of different ages, different backgrounds, different attitudes, but again, with the common thread of wanting to work together, not wanting to impose their vision, actually wanting to come up with something that would work. So that's what I would want, people of different ages and, different motivations, but with the same spirit of doing something that is not just trying to fulfill their immediate selfish needs, but something that should function usefully for centuries to come. Ned Grady says, "Why should we be excited about entropic gravity if the general relativity equations pop out of it? I thought we know that GR isn't the final answer."

1:17:49.5 SC: Well, the idea would be that something like tropic gravity, which as currently stands is a little ill-defined, but that it could be the final answer, right? That it is more fundamental than general relativity. That's the idea. Or maybe it's a stepping stone to something even more fundamental. I tend to think that tropic gravity, like I said, is not very well defined by itself, but is a way of thinking about what gravity might be, right? That it's a shift from kind of a mechanical view of the world where things are pushing and pulling like rubber bands and springs to this more thermodynamic view of the world where you talk about probability distributions and likelihoods, and thermodynamic variables changing with time. It's a change of perspective that might help us get to what is the ultimate theory. I don't think we have any idea what it is right now.

1:18:38.6 SC: Or let's say we don't know what it is right now, even if we have good ideas that might eventually turn out to be the right ones. Spencer asks a priority question, "Could you please share your experience or perspective on burnout in academia? Specifically, how do you disentangle burnout from a lack of passion in your field of study?" I'm honestly not the person to ask about this. I've certainly myself never, burnout is not my worry. Let's put it that way. I have worries, I have issues with academia, with my lifestyle or whatever, but my issues tend to be I don't have enough time to do all the stuff I wanna do, rather than I'm burned out from doing the stuff that I wanna do. Having said that, it's absolutely an issue. I'm not trying to, dismiss the reality of this problem because people are different and, people are going to have different issues, different difficulties in dealing with the challenges of academia.

1:19:32.2 SC: Academia, like we said before, is something that many people wanna do. So part of me wants to say, "Don't forget how hard you worked for this." Another part says, "Look, I know people who are super successful academics who do get burnout and don't wanna do it anymore. And that's fine." So one little tiny piece of advice about burnout is maybe it's good that you're burned out. Maybe you have realized you've come to a, an epiphany that says, this is not the thing I wanna be doing. That's okay. It's tough because academia is a little bit of a one way street, right? You can be in academia and leave. It's very hard to leave and then come back or just be wildly outside and then come in. But also it's possible that the burnout is just temporary. Maybe the thing to do is to stay within your department, but change your research focus a little bit, right?

1:20:31.6 SC: Maybe the thing to do is to take a sabbatical and do something very different. Maybe the thing to do is concentrate on teaching for a while. Maybe the thing to do is just take a vacation for a month and not think about academic things whatsoever. Like I said, I'm not, this isn't my problem. I have other problems, but, it's a real problem. So I think that you should look for more helpful resources than the Mindscape AMA. Sorry about that. David Maxwell says, "You remind us that physics is maths, not the narrative explaining it. It reminds me of non-native speaking expats who internally live translate until it's embedded. They fully switched when they dream in their new language. When do the... " Now we finally get to the question here. "When you do the thinking part of physics, is it in language or is it in equations? Do physicists dream of equational sheep? Well, it is true that the ultimate final statement of a physical theory tends to be in terms of the mathematical equation, but it doesn't mean that the way you get there is via mathematical equations.

1:21:42.2 SC: Different people have different techniques, it's an oversimplification, but roughly speaking, there are people who sort of think more formally and in equations, and there are people who think more pictorially and in pictures, right? In diagrams, in images or things like that. And actually, I'm more on that side. So it is absolutely true that when I'm deep in a physics thought, physics paper, or something like that, I will dream about it. Just last week, I was laughing when I woke up because I was so deeply thinking about this paper I was working on. But it's not in terms of equations, it's terms of pictures or symbols or questions about what fits together in certain ways, graphs and so forth. I would be not at all surprised to learn some certain other people do dream in terms of equations, probably not that effectively. But if that's how you think, then that might be how you dream. Gregory Kusnick says, "As an academic you of course have social connections all over the world, are your local connections in Baltimore primarily within the university or have you found ways to connect with local people independent of your job? What advice do you have for someone settling into a new city without a ready made social network?"

1:22:58.4 SC: Yeah, I think it's a combination and I think it's a little bit unpredictable. In LA, where we lived for over 15 years, our social circles were pretty non academic. I didn't really hang out that much with people from Caltech, with some people I did and I love my Caltech colleagues, nothing against them at all. It's just that for whatever reasons of demographics and whatever, we didn't socialize that much. My social circle was made of people I met randomly at different things, through projects like the Science Entertainment Exchange or just normal human interactions like meeting someone at a party. Jennifer and I, one of our closest friends we met because the if you... Jason Torchinsky who is a former Mindscape guest and also the illustrator for some of my books, he used to live in LA and he moved away. So we went to his going away party and many of the people there had little children. And so the few of us who didn't have little children bonded together there at the party and we met some of our closest friends at that particular event. So I can't predict that ahead of time, right? Here in Baltimore, it's a little bit different, I am sort of closer on a social level with several of my colleagues at Johns Hopkins.

1:24:16.5 SC: And part of that is the circles in which I move at Hopkins are much broader than at Caltech, Caltech is a, I love Caltech and it's a great place and it's very much stay in your office and do your research kind of place. Whereas at Hopkins, the fact that I can be so interdisciplinary and I get to meet people in other departments in political science, in engineering and whatever gives me a great much greater chance to meet people of different interests that I might sort of match well with socially. But we also... It's a different place, we are very good friends with our next door neighbor, okay? Who is sort of like the boss of the neighborhood and he introduces us to people, and his next door neighbors so the other people down the corner own the local restaurant that we can walk to and have drinks and dinner and so forth. So we've become friends with them, obviously, it's in our interest to become friends with the local restaurant owners and that has worked out very well. So yeah, I don't think that there is an algorithm for doing that other than being open minded. Yeah, being open minded is the big thing, it's like the dating advice, the relationship advice we had either last month or two months ago.

1:25:30.0 SC: The failure mode is to say, "I wanna find my life partner, I'm gonna do that." I think that's maybe not quite as strongly but it's still true just for finding friends in different environments. If your purpose is to find friends and you're sort of goal oriented in that way, I think you'll be less successful than if your purpose is just to like meet people and talk to them and learn about them. Are they interesting? Why are they here? Why are you in the same milieu to in the first place? What do they have to offer? What interesting stories do they have to tell? Some of them will not be your friends, some of them could be your bitter enemies, you don't know. But if you go in with the attitude of learning about people and having a good time rather than finding friend, I think that it is much more likely to succeed. Eric Schrader says, "Do you think there's a way to incorporate general relativity and Quantum Field theory into undergraduate physics? I have a bachelor's and love hearing about these topics from you and others but wish it were taught to me back in my college days." Well, it depends on what exactly you have in mind.

1:26:39.9 SC: So one approach would be to try to teach them at a kind of survey level to non physics majors or non science majors. I'll be trying to do that this fall, I'm actually gonna pioneer a course for non physicists at Hopkins, to fulfill science breadth requirements based on the first two volumes of the biggest ideas. So we'll be doing classical mechanics, relativity, quantum mechanics, Quantum Field theory. I have no idea how good it will go or if it will go well at all. I think it's easy to see how best to explain it, I've already written the books, the difficult part will be tests evaluating, right? Beause I can't just give out problem sets 'cause the whole point of the books was not to teach people how to solve problems on problem sets. So we'll see how that goes. But I think what Eric has in mind is for physics majors, general relativity is very easy to incorporate into undergraduate curricula, I've done it. I pioneered at University of Chicago before they let me go an undergraduate course in general relativity that was a huge success, and I think it's still being taught there. It's not that different to be honest from the graduate level course, a little bit less of the notation and mathematics, but not too much less of it.

1:27:50.0 SC: I think that the difference between undergrads and grads when it comes to general relativity is not that you need prerequisites to get to general relativity, but you have to be able to sort of be tough enough to be faced with a whole bunch of new notation, new ideas very quickly and absorb them. But it can be done. Quantum Field theory much harder to do with the undergraduate level. I think that what typically happens and can work very well if you're at a university that has a graduate program is that Quantum Field theory, which is generally by the way, a year long course, and you still don't get the whole standard model finished, unlike general relativity, which is either a one semester or one quarter course. Teach that at the graduate level, and then if you have a sufficiently advanced or ambitious undergrad, they can take the course. That's the best way to do it, I didn't have that when I was an undergrad, but I think that a lot of undergrads are able to do that. And that's probably the right thing to do, there's just too much there in Quantum Field theory to make it a regular part of the undergraduate curriculum. Steve Odendall says, "Are there any scientific theories you find particularly elegant or inelegant."

1:28:58.0 SC: "Between two competing theories for the same phenomenon, assuming all else is equal? Do you think the more elegant one is more likely to be true?" Yeah, there's plenty of theories that are elegant or inelegant, and it might very well be in the eye of the beholder. I think that many-worlds as approach to quantum mechanics is very elegant, it's just the Schrodinger Equation and thinking hard about the implications of that. Whereas I think the leading contenders to be alternatives to many-worlds, things like hidden variable theories or objective collapse theories are ugly, they are inelegant, they're just adding these things to try to explain what you think is the data, right? Of course, it's also very plausible that you find a theory that is inelegant at the moment, because you don't understand it all the way. So maybe there's some future principle that makes these currently inelegant looking theories looking very beautiful. So you can't take that as too definitive about accepting a theory or not. I would take at any one moment, if you had two theories that were both equally good at fitting the data, the more elegant one to be higher credence to be more likely to be true. But I think it's a little bit missing the point of elegance elegance plays a huge role in theoretical physics.

1:30:13.0 SC: But it doesn't tell you what is true, it tells you maybe, it suggests to you where to look for truth. The thing about physics is that as we have discovered more and more successful laws of physics, they turn out to be elegant. So looking for things that are elegant and beautiful, and especially things that can explain many different phenomena using a small number of underlying simple principles, seems empirically to be a successful way of doing physics. It doesn't tell you what's true, but it can help you suggest things that might be true, and then experiment tells you what is true. Okay, I'm gonna group together a whole bunch of questions, four questions. I think I struck a nerve somewhere, but you'll see what they're about. Tarun says, "In the June AMA, you mentioned that you'd be happy to step into a teleporter that disassembles you on one side and reassembles you on the other side with different atoms as the reassembled person would still be you. Surely you would not be okay with a perfect clone of you being created with all your memories and then the original you being killed a second later. Given the same effective outcome, why is the teleporter any different from this clone scenario?" Matthew Clifford says, "I discovered your podcast last year and been really enjoying the catalog of back episodes."

1:31:28.0 SC: "I've come across two instances where you've been asked the classic question of whether you would have any qualms about using the Star Trek transporter, which converts one's body from matter to electromagnetic energy and then back again. Both times you based your answer on your firm belief that consciousness resides solely in the unique arrangement of atoms and molecules within your brain, and not in something more mysterious or supernatural. You confidently stated that you would have no problem using the transporter provided your unique pattern would be faithfully reestablished upon your arrival. Because this would necessarily preserve your conscious mind and the continuity of thoughts as though nothing had happened. But would it? Even if one accepts the premise that consciousness is purely a physical phenomenon, does it follow that if your body were destroyed and reassembled, you would subjectively experience that process as a continuation of your own stream of consciousness. Consider the fact that if the technology existed to reassemble your body with that degree of precision, it would be equally possible to assemble multiple such copies of your bodies, each with exactly the same arrangement of atoms."

1:32:28.8 SC: "Would you then simultaneously experience the separate thoughts of each of these copies that seems implausible?" Gary says, "I have a twist on the teleportation paradox. Suppose a futuristic villain would without your knowledge scan your exact molecular composition and create a computer simulation of you being tortured, would you find this threatening?" And then finally, Chris Gunter says, "I think I caught you in a logical contradiction. This is in regards to the Star Trek transporter question, you said you regarded the person coming out of the other end as yourself, because there is continuity of pattern throughout the whole process. However, you've also said that while when the universe splits, there is one branch that has you and another branch that has someone like you, but not you." And then Chris goes on to explain that this is a contradiction. So you see the common thread between these four questions all about the plausibility or how we should think about transportation, transporter machines or duplicator machines and so forth. So let me say two things, preliminary to actually answering the question. One is, yes, I absolutely stick by my opinion that what matters is to personhood is continuity of psychological experiences, not some mystical essence that floats from our body from moment to moment.

1:33:51.7 SC: So yeah, I'll just leave it at that, I'm gonna stick by that and then I'll elaborate it in a second. But the other thing is, which doesn't get talked about in these scenarios very often is and you get sentences like Matthew saying, this sounds implausible, [laughter] and so forth. Because these scenarios are nowhere close to the real world, right? We don't experience anything like this, the real world as it actually is right now, not possible future worlds, but none of us has experienced being in a transporter machine or being duplicated atom by atom, et cetera. So what is happening in these questions is that we're taking our intuition of what it is like to be a person, which is entirely 100% shaped by our experiences of living from moment to moment as a single human being and not experiencing splitting or transporting or anything like that. And we are trying to extend them to these different kinds of situations. There's no reason why we should trust our intuitions in these wildly different situations. So in some sense, there's no right or wrong answers, these scenarios are truly new, right? Things that have never been experienced before, you're welcome to have your opinion about them.

1:35:12.0 SC: All I would say is that it is dangerous to think that I can sort of straightforwardly take what I believe and feel about my life as an ordinary human being and apply them to these very different situations. Final thing I will say is a footnote before actually answering the questions. Let's answer Chris's question first. He is, thinks there's a contradiction between my views about many-worlds and my views about the transporter. But he says, I think that he says something that I would never say. "You've also said that when the universe splits, there is one branch that has you and another branch that has someone like you but not you." I would never say that, at least maybe I have said it, as we'll say, as we'll see further down in the AMA, who knows what I've said over the course of many things, I can misspeak or I can be imprecise trying to say something that I do believe but not saying it very correctly. The point is not that when the universe splits, there's one branch that has you and another branch that has someone like you but not you, that is absolutely not what it is. Once the universe has branched, there are now two people, let's imagine the simplified situation where there's one person which is you.

1:36:25.0 SC: You measure a spin and now there are two branches with two people, on each branch, that person is themselves and the other person is not themselves, [laughter] is not the person on the first branch. So what I'm trying to say over and over again is the two people on the two branches are separate people, right? They can't communicate with each other, they share a common past, but they have no influence over each other, they don't share common futures and so forth. There's not a fact of the matter about which one is you, that's completely false, there is not some essence of you that traces through all the branches of the wave function. The metaphysical demand of believing in many-worlds is that you have to dramatically change your conception of what it means to be a human being over their lifetime. In single world scenarios, a human being over their lifetime is a single entity with one sort of little pink world line, right? World worm that people sometimes call it. Whereas in many-worlds, it's a branching tree where there's one past and many, many futures, okay? So that's a dramatically new thing that our intuition is not equipped us to think about very carefully. If we go to the other questions, let's see if I can do this very quickly, so I don't wanna spend too much time on this.

1:37:46.0 SC: "Surely." Tarun says, "You would not be okay with a perfect clone of you being created with all your memories and then the original you being killed a second later." I would not be okay with that, but I would not be okay with it because of the phrase a second later. If it were instantaneous, then I would just say that I had moved from where I was to somewhere else. In other words, think of it this way, it's perfectly okay to think of ordinary evolution through time as getting rid of your old self and having a new self come into existence, the self I was one second ago no longer exists, now there is me, so now there is me now, right? So the thing that I'm trying to get rid of is this idea of some essence that is continuous through time, what exists at each moment of time are configurations of matter and energy that collectively make up myself. And again, in the real world, that in the real world of our experience, where we don't get to see the other worlds of quantum mechanics, that is a unique thing that passes from moment to moment, we have to update our notions of what's going on when you invent these science fiction scenarios about creating identical copies.

1:39:07.7 SC: The thing about making a clone of you and then original you being killed a second later, which is not the same as yourself just evolving through time, is that that other self existed for a second and then died, right? That's just as bad to me as myself dying a second from now, but it's not because there's another one, it's nothing to do with the other person over there. How do you know that the universe isn't? If maybe we live in a simulation and someone is turning off the computer and starting it up again, and there's this period of time where we all died, and then we were reincarnated, right? This is just meaningless, this doesn't make any difference to our lives and my point is that if there's an exact copy of you, literally an exact copy of you, then that's exactly the same kind of person that you were. And killing either one of those copies is bad and having either one of them should have the same rights and obligations that you do. But if your scenario is that there is only ever one of you, and that one of you just gets teleported or whatever, I see no problem with that. That I don't see why I should mind, why should I mind that at all? It doesn't change my life experiences other than it's much easier to get across the country.

1:40:22.5 SC: I'd like this scenario. Okay, what was the other question here? Yes, Matthew is asking about, let me get it right here. What is the middle of the question here? "Even if one accepts that consciousness is a perfectly physical phenomenon, does it follow that if your body were destroyed and reassembled, you would subjectively experience that process as a continuation of your own stream of consciousness?" Again, if you really wanna take these questions seriously, stop using the word you, [chuckle] because you're implicitly assigning some essence to this continuity over time. I don't think that that exists, I don't think that's... It does exist in the real world, but it does not... You've invented these hypothetical scenarios where it ceases to exist. In this scenario, where you can sort of be destroyed and exactly reassembled, that reassembled thing would be indistinguishable from a version of you that had never stopped existing. So I don't see why I should treat it any differently and the fact that it seems implausible doesn't really change my mind very much. Could you make multiple copies? Yes. And then you'd be in a truly unique situation where there were multiple copies of people who started out as exactly identical, literally the same person.

1:41:49.4 SC: But then as soon as they interact with the world and each other, they now become different people. There's no such thing as which one is the right you, but they're all people that is almost exactly like many-worlds, except that you're giving the people the actual opportunity to interact. So it's even more obvious that they are separate people, not different copies of the same person. Oh, yes. And finally, Gary's question, which I like because Gary's question is a good twist on the paradox, the villain that could scan my exact molecular composition, create a computer simulation of me being tortured, would you find this threatening? So this is actually something I hadn't thought about, which is why I like the question. Threatening is not the right word, I find it bad, and the reason why I find it bad is because if you grant the assumptions of the thought experiment where this computer simulation truly is an exact copy of me. Now there's a person being tortured, right? To be consistent with everything that I've said before, there's no principled way of saying which one is me and one of them is being tortured and I think that's bad. So finding it threatening is not quite the right language to use, because it's not that I will be experiencing this.

1:43:05.7 SC: But that there's a person who shares a past with me who's experiencing this, there's no such thing as the unique me in the future. But still, that future person, I feel bad about them being tortured, so it's not that it's threatening is that it's bad. That's how I would put it. Okay, I gotta start giving quicker answers to some of these questions. I'm sorry, we're going very long here. Lishan Aklag asks a priority question, "In something deeply hidden and in numerous AMAs and podcasts. And now in quanta and fields, you made a consistent compelling case for that the underlying math strongly supports the Everett plus decoherence formulation of quantum mechanics. You've made me into a solid Everettian, albeit one who is looking forward to a more complete understanding for you and others of the emergence of our space time reality. The question is, is there a reason why that a relatively simple neo-Copenhagen formulation hasn't taken root, one which accepts most of the underlying mathematical formalism, but postulates that decoherence selects just one branch with born rule probability of the wave function, instead of branching it." Well, you are welcome to try to invent such a theory. But it is a very, very different theory.

1:44:18.0 SC: Essentially, that is objective collapse models, right? Because if you just have the Schrodinger equation, and you just have decoherence, you get many-worlds, everyone agrees with that really. You might not like it, you might not think it's a coherent scientific theory, but that's what the Schrodinger equation predicts. So you have to change the Schrodinger equation, it doesn't matter that you have decohered, you have to decohere and then change the evolution of the wave function so that there's still only one branch, okay? So that's basically a version of objective collapse. But then what is triggering the collapse? What are the equations for it? All that has to be developed. And the way that people have done it is leads them to either some sort of triggered collapse, a la Penrose, or some sort of random collapses, a la GRW. None of them are very compelling, they're all sort of ad hoc and weird and to me, no need for it because many-worlds works perfectly fine. Zach McKinney says, "In view of the decline in public trust of rigorous science as a shared epistemic basis for what is, how important do you consider it to restore public trust in science and a shared consensus reality."

1:45:25.0 SC: "Relative to improving cultural coherence around some shared human values?" Well, I'm not sure that public trust of rigorous science as a shared epistemic basis for what is has actually declined. Maybe it has, I think that would be something that would be very hard to objectively measure, people in the past believed all sorts of weird, crazy, non scientific things, right? But basically, I'm gonna give a disappointing answer to this, because I absolutely believe that we should work hard to improve trust in science, not absolute blind trust, but sort of an idea that scientific experts know more than non experts about scientific questions. And so your credence should be high to in areas that you are not yourself an expert in, believe that they are more likely to be right than you and therefore to put high credence on what they're saying. How to make that happen I truly do not know, this is an empirical question, this is a question that many people know more about than I do. Okay, so it's exactly the kind of question that I want to resist the temptation to say I think it's very important, but then not to do the work. In other words, to just say, "Hmm, let me think for five minutes about how to make scientists be more trusted in the world and then spout my opinions about it."

1:46:43.1 SC: This is something where we need to do the work, we need to do the scholarly effort, trying new techniques, seeing which ones work seeing which ones don't. And people do this, I don't do it myself, so I'm not the person to ask, so I'm in favor of it, but I don't have a favor way of making it happen. Nathan says, "I've been enjoying Quanta and Fields, in chapter nine, you explain how the reason that photons are massless can be considered a consequence of gauge invariance. This explanation relies on the fact that the vector potential is a real valued vector field. But I did not understand why we asserted that it is real value, especially while we were letting the components of the electron field be complex valued." So yeah, for those of you who have not read the book, this is gonna make no sense at all, or at least unless you know something about Quantum Field theory. But you don't just get to pick what the variables are that represent these different fields, you can always start by picking some fields like here's an electron field, they need to have some if just to say that it is an electron field is meaningless. What you say is it has some geometric properties, right?

1:47:50.3 SC: So it has some tensor structure or some spinner structure or something like that, complex value to real value, you can start with that. But the gauge potential, which is the field that gives rise to the photon isn't just something you invent, it's something that comes out of a line of deduction from saying that I would like a certain symmetry to be respected by my theory, how do I do that? And the intuition is that the gauge field is basically balancing out what is being done to the original field you started with the electron or whatever, by the derivative, okay? You take a derivative of the field respect to space and time, partial sub mu in mathematical language, and you find that that thing is not gauge invariant, so you have to correct for it. So you don't have any freedom to ask whether or not the gauge field should be real valued or complex, it has to be what it has to be to make sure that the thing you're constructing is gauge invariant. And because the derivative is a real valued thing, you're taking derivatives with respect to space and time, which are real valued variables, not complex valued variables, it turns out that the gauge field also has to be a real valued variable.

1:49:05.5 SC: I'm saying this very tentatively, because of course, you're welcome to invent whatever theories you want. But that is the way it works out in the conventional theories that people learn about in their Quantum Field theory class. Raj says, "While the conventional process of debating new ideas and sciences still through publications of papers and getting them peer reviewed over many years, there's a growing number of YouTube channels often run by scientists or groups of experts that put forth new ideas. Sometimes these videos add value through excellent visualizations of concepts, have you seen such a move in your field? I wonder what this democratization of academic publication process would do to your field?" No, I've not really seen that very much in my field, of course, YouTube is open to anyone to get on and say whatever they want. But it hasn't made much of an impact on the not only my own area of science, but any area of science that I know about. The barrier to saying things on YouTube is much lower than the barrier to making a real scientific contribution, let's just put it that way. I do think that new technological tools might be very useful.

1:50:10.8 SC: But the idea of filters and hurdles and expertise and things like that that goes into the conventional scientific discourse have value for real reasons. There's a large number of people out there with crazy ideas, you need to have ways of figuring out which ones are worth paying attention to. William says, "Red or green chili?" This is a question for New Mexicans, if you're not someone who spends time in New Mexico, you should learn if you ever come to visit that the state question is red or green. And it refers to what color chili you want on your burrito or your other dish. Chili in this case is not like Texas chili, like meat and beans and things like that, like kind of a soup that you eat as a meal by itself, it's a sauce. It's a chili sauce that you make out of chilies, but also chicken stock and spices and things like that. And if you do it, let me... I'm not sure if I get it right. Red or green are the same kind of chili, but just picked at different times. Okay, the colors of the actual chili plant changes over time. I'm a red chili person, the flavor of red chili just is much better to me and sometimes I will do what is called Christmas, which is both red and green. But mostly red is a pretty easy decision for me.

1:51:31.5 SC: I don't even understand green chili people, they're just weird. Ted Williams asks a priority question. "I've heard a few times that we are puzzled by the fact that the universe began in an extremely low entropy state, which makes sense if I think of it from the context of an outside observer. But I don't understand why that isn't just explained by the anthropic principle." Oh, easy, because the entropy could have been much, much, much, much, much larger than it actually was and still be completely compatible with us human beings here on earth. There's different ways of explaining this quantitatively, but just think about what you need to make human beings, right? Maybe at most you need like the earth and the sun and the planets in the solar system, you don't need the rest of the galaxy. You certainly don't need 200 billion or a trillion other galaxies, and you certainly don't need all those galaxies to have been, all the matter in those galaxies to have been configured in some extremely low entropy state at early times. Now, people will say, well, you do need all that, you need the whole evolution of the universe to give rise to heavy elements and things like that or whatever you need for life on earth, tidal forces or the moon or whatever.

1:52:41.8 SC: But that's wrong, you don't need that you think you need that because you're assuming conventional thermodynamic evolution from an initially low entropy state. But it's much easier just to have a random collection of particles assemble themselves into the form of the earth and the sun and whatever chemicals you need to make life go. It's a much, much, much easier thing to imagine from purely an entropic point of view than the actual low entropy of our early universe. There's an order of asking questions here, given that the entropy of the early universe was extremely, extremely low there are various plausible things you can say about what is more likely than not to follow from that. And it was more likely to get human beings as the result of billions of years of biological evolution, then randomly coming into existence given that low entropy past. But objectively speaking, in the space of all possible pasts, that low entropy past is much, much, much less likely than human beings randomly fluctuating into existence. So the anthropic principles of no help explaining whether the early universe had low entropy. Andrew Goldstein asks a priority question, "Relating to your excellent podcast with Samir Okasha."

1:54:00.8 SC: Okasha, I should say, "About agency and evolution, could thermal gradient reduction be a teleological basis for the evolution of natural processes in non equilibrium thermodynamics? For example, simple processes like Bernard Rayleigh convection increase heat transfer efficiency. Do you think energy gradient reduction is a fundamental driver of emergence at all levels of physical, chemical and biological complexity?" No, in fact, it's clearly not. So there's actually like a whole... I forget who wrote it, there's a whole book about the idea that the whole point of evolution, not biological evolution, but a physical evolution was to reduce entropy gradients to smooth things out. And you could see why people would think that, if you start in an ordinary chemical or fluid mechanical system, and you have a low entropy state evolving into a high entropy state, the high entropy state is usually more uniform, right? Low entropy state might be lumpy and things smooth out. But there's counter examples to that and especially vivid counter examples such as the universe, [laughter] the early universe had very little entropy gradients, very little temperature gradients, I should say, it was more or less the same temperature all over the place.

1:55:16.0 SC: And the temperature gradients increased, they didn't decrease. Why? Because there's something called gravity, and gravity is important. Unless you think that gravity doesn't exist, you can't claim that there's any principle of evolution that smooths out temperature gradients over time. You need to think more carefully about what is really going on and that's what we're trying to do. People are trying to do that, but it's hard, it's a complicated problem. Mikhail Maliki says, "Some popular science figures claim they are instrumentalists about science, I have a hard time believing that when it comes to science dealing with large objects. However, I'm wondering if folks working on subatomic physics are mainly instrumentalists or realists. What about you, are you an instrumentalist or a realist all the way down?" I'm 100% a realist, people who believe in many-worlds are tend to be cheerful realists about the wave function of the universe, which is the most fundamental thing that we know about. I think that instrumentalism in the sense that we're not really invested in the ontological reality of the scientific entities that we propose, we're just using them to make predictions for experimental outcomes.

1:56:29.0 SC: I think that's just a bad attitude to have 'cause number one, it's not true, you really do care about what is going on in reality, at least I do, I care. And number two, it's not fruitful, the more real you take these entities that you think about, the more likely you are to understand them better and use them better to predict new theories in the future. Now there are subtleties dealing with the fact that as we improve our scientific understanding, we often change our favorite ontologies. If you go back to the podcast we did with James Ladyman a while back, he has this idea called structural realism, where you can believe in the structures of your theories, even if you actually replace the objects that your theories posit with better an understanding of what the objects are. So I can absolutely be that kind of realist, I am a structural realist all the way down. Simon Huntley says, "Could you provide a good summary answer as to why finding a magnetic monopole would be a big discovery?" Well, the short answer is 'cause we've never found one, and in physics, when you find something that is absolutely new, that is necessarily going to be a big discovery. Now there's a longer thing to be said here.

1:57:40.0 SC: In nature, you have an electric field and a magnetic field, they are combined in relativity and electromagnetic field. But there's a symmetry, they seem kind of similar to each other, electricity and magnetism. If you lived in a world without charges, okay, if you lived in a world without charged particles, if you had Maxwell's equations for electromagnetism, but with only the electric field and the magnetic field, not with charged particles like electrons and things like that, then these equations are completely symmetric. Under replacing the magnetic field with the electric field and vice versa, this is called electromagnetic duality of the vacuum Maxwell equations. That's a symmetry, whenever you can replace one thing with another without changing anything, that's a symmetry. It is broken by the existence of electric charges, there are electric charges, but not magnetic charges, as far as we know, in nature, that breaks the symmetry between electricity and magnetism. So it's very, very natural to wonder, why aren't there magnetic charges in nature? And the first really serious thoughts about this were from Paul Dirac, and he showed that you could actually imagine magnetic monopoles.

1:58:55.0 SC: So by a monopole, we mean an object that has one polarity, so it's a single charge. So in electricity, you have positively charged particles like protons, negatively charged particles like electrons, those are both electric monopoles, they're either plus or minus. In magnetism, you have dipoles, you have a little magnet with a northern end and a southern end. But you don't have monopoles, you don't have just a particle that is like a northern magnetic field that acts as a source for lines of magnetic field, like you have particles that act as sources for electric fields. So Dirac showed that you could mathematically consistently talk about these things. It was not easy, there was a little sleight of hand, there was a singularity, et cetera, and people weren't sure whether to take these seriously. Then along comes the 1970s and '80s, when we learned that electromagnetism is just a smaller part of a much larger group of symmetries in the standard model of particle physics. And people in the '70s in particular said, "Well, let's continue this project of unifying symmetries." And they invented what is called grand unified theories, where they unified that electromagnetism and the weak force with the strong force of particle physics.

2:00:11.0 SC: And it turns out that these grand unified theories predict the existence of magnetic monopoles. In fact, according to the best cosmology of the time back in the 1970s, they predicted way too many monopoles, you could even predict their masses, they'd be very, very heavy, the abundance should be very high. This was a problem for grand unified theories cleverly called the monopole problem. And it was the single biggest motivation behind Alan Guth proposing the inflationary universe scenario. These days we think of the role of inflation as making the universe smooth and spatially flat. But the original thing was dilute away the magnetic monopoles, if you made monopoles in the early universe and then inflated them away, you could be consistent with what we observe today. So discovering magnetic monopoles would both be intrinsically interesting because discovering anything we don't know about would be very important. But it would also suggest that maybe they are a relic of unification of the forces at very early times. To know that you would have to actually study the magnetic monopoles you discovered, and we'll see whether or not that turns out to be the right answer or not. Brendan says, "I've heard some theologians argue for the existence of a God based on how intricate DNA appears to be."

2:01:29.7 SC: "A common example seems to be that if you came across a written book, you would have a high degree of confidence that it was written by someone. This line of reasoning is then applied to DNA as it could be considered a language too, for you, does the complexity of DNA increase or decrease your credence for a God." No, it does not change my credence in the existence of God at all, because we have a perfectly good theory without invoking God that explains why DNA is here. If DNA just spontaneously appeared out of nowhere, then yes, you might have a case for imagining that we needed to extend our ontology into theological realms. But we know that didn't happen, we know that there's something called evolution, that the DNA of biological organisms used to be smaller and simpler and has developed over biological time to be what it is today. So I don't think there's any reason at all to give God credit for that.

2:02:25.0 SC: Sandra Stuckey says, "What was the most exciting thing you just learned or discussed at the Santa Fe Institute?" So I'm recording this from Santa Fe, New Mexico, where I'm doing my biannual visits to SFI. Well, this, you're gonna be surprised by this. The most recent interesting thing that happened was on Friday, I guess it was Friday. We had just gotten the results of the elections in the UK, which were good for the left hand side of the political spectrum. And we happened completely coincidentally at SFI to be visited by a member of the House of Lords, Lord Alderdice, who is a Northern Irish politician and a very smart guy who was an academic for a while before he went into politics. And he studies conflict resolution and in particular, seemingly intractable political violence. And he became interested in this from the Santa Fe perspective, right?

2:03:25.5 SC: From the complex systems perspective. Are there things you can learn about complexity and complex systems that can help us overcome seemingly intractable political conflicts? There you go. So we happen to be visiting SFI when the elections happened. And so Sam Bowles, previous Mindscape guest, who is a resident faculty here at SFI, organized a little tea time conversation where Lord Alderdice, despite being the House of Lords, he's a very nice down to earth person. And he gave us a little overview of the election results in the UK, what they mean, what they mean about politics more generally. We talked about first pass the post voting versus ranked choice voting because one of the things about the UK election is it was actually very tiny shift of votes in the direction of the liberal side of things, but a huge shift in the representation in parliament.

2:04:18.8 SC: And the reason why is because of the voting system that they use in the UK, which is, by the way, the same voting system we mostly use here in the US, first passed the post or just, there's another name for it. I'm forgetting the names right now. But the point is, whoever gets the most votes wins, right? The problem with that idea is that if you have a whole bunch of districts, there's also geographical representation playing a big role here. So you have geographical representation. If you have a whole bunch of districts where it's 51% for one party and 49% for the other, as long as it's the same party that gets 51% nationwide, you get a 100% representation for that party, even though the nation is only 51%. And a 2% change in the popular attitude can mean a 100% representation for the other party.

2:05:13.5 SC: So this is fascinating stuff for people who think about complex systems and in particular, the physics of democracy, right? As well as for people who care about current events. So it's just a quintessential SFI kind of interaction where, oh yes, we just happen to have someone here who's a member of the House of Lords who is thought scientifically and intellectually about how these systems work. And we can sit around at tea time and have a interdisciplinary conversation. Anyone is invited. That's what makes SFI kind of my favorite, my intellectual playground above any others, really. Okay. I'm gonna group a bunch of questions together, and, yeah, I'll just read them. I can't really summarize them. They're about particles and fields. So Nicholas Weinberg says, "I'm reading Quantum in Fields with great interest. You describe how quantized particles appear as solutions to continuous equations. And a critical step for this to happen is to restrict the solutions to where the wave function keeps its shape as time passes, and where the energy has a definite value. Are these restrictions motivated by something except that they cause particles to appear in the solution set?"

2:06:25.6 SC: Dodds Odds says, "I'm going to have another run of the question of the emergence of particles from fields." In quantum and fields you describe how a particular pattern of modes a wave packet can look like a particle, no problem with that. But what I'm missing is why a wave packet would be a common pattern of modes for us to encounter in the world. Surely a wave packet is only one of an infinite number of possible collections of modes that a field could be excited into. And then finally, Henry Jacobs says, "In quantum fields, I just finished the section where you illustrate how particles with definite momentum emerge from a scaler field. Lovely. Now, if I observe a particle that is localized in space, it has an infinite number of fourier modes, is observing a single particle with a definite position the same as observing an infinity particles of definite momentum."

2:07:09.0 SC: I've totally confused myself. So these are all, I do apologize to the listeners who have not read Quantum and Fields, but I think that the people who are good enough to read it, I should give some attention to them and try to answer their questions. So this is actually, these questions are more subtle than you, the questioners themselves might even know. So if you take a course on Quantum Field theory, you'll be taught what I teach in what I go over in the book, which is that if you have a simple quantum field, no interactions, no spin, what we call a free Klein-Gordon field, and you quantize it, so you feed it to the Schrodinger equation, you have a Hamiltonian for it. You construct wave functions, you let them evolve with time. You find that the solutions to the Schrodinger equation come in this series, right?

2:08:02.5 SC: There is a single unique vacuum state where there are basically no oscillations or no energy, the lowest energy state of all the different modes of the field. But then there are excited states, and these excited states start by being discreet. The lowest excited state has an energy of at least the mass of the particle or more. And we interpret that as saying it could be a particle at rest whose energy is exactly the mass E equals MC squared, C equals one. Higher energy versions are that particle is moving, it has momentum, and so now it has kinetic energy as well. And then there is another series of solutions to the equation that look like two particles and three particles and four particles, et cetera. So the particle ness pops out of the fields just by taking the rules of quantum mechanics seriously, that's what you would be taught.

2:08:53.5 SC: And that's true, and that's what I say in the book, to make that happen. So you notice that I talked about the solutions to the Schrodinger equation, but guess what? The Schrodinger equation is linear, which means that I can take any two solutions and I can add them together, or I could take any number of solutions and add them together, and the answer is still a solution. So there are these special solutions to the Schrodinger equation. This is what Nicholas is getting at in his question, which have definite amounts of energy, and the wave function keeps its shape as time passes. But there are other solutions too, [laughter] where the wave function does not have a definite energy, does not keep its shape as time passes. What about those? And this is very related to Dodds Odds' questions, "Why wave packets?" And Henry's question, "Why isn't it just an infant number of particles when I localize it in space?"

2:09:49.7 SC: So the point is actually not discussed in a typical quantum field theory course, and it has to do with, guess what, the measurement problem of quantum mechanics. So yeah, if you just have a quantum field out there, if you have a single electron, you make an electron, or let's, let's say you make a photon. 'Cause making electron requires you to say where the electric charge came from, et cetera. But you make a photon, okay? The wave function of the photon will generally not be localized in space or in energy. It'll be spread out all over the place, okay? Or the photon fields wave function will be a superposition of many different numbers of photons, and it'll be spread out all over space. But when you observe the photon, you don't see that. You see the photon having some location. So very often in the discussions of this, we say, let's imagine we have a wave packet.

2:10:47.5 SC: It's not that we actually do have a wave packet. By a wave packet, we mean a situation where the actual vibrations in the wave function are centered around some point and relatively localized in space. If the field is completely free and not interacting with anything else, you're unlikely to get that kind of behavior. But when you observe it, it looks like you have that kind of behavior. And if you actually do something like send the photon through a detector that can let the photon travel, but keep track of its trajectory, then what are you doing? You're continually observing it and basically making it look like a particle, making it look like through the process of measurement and decoherence and wave function collapse, a wave packet like thing moving through your detector. As far as the energy I states are concerned, it's a similar kind of thing.

2:11:40.5 SC: Systems, it's actually easier to think of an electron in an atom, but it's a very similar thing for modes of a quantum field, electrons in atoms, if you ever took your chemistry class, we talk about the orbitals that the electron could be in, right? The lowest energy orbital, the next energy orbital, et cetera. When the atom is in its ground state, you've filled up all, all the electrons you have in the atom have filled up the lowest energy states that they could be in. But you can easily imagine an atom that is not in its lowest energy state, but what happens if a electron is in a higher energy state than it could be in it will decay, it will give off a photon and go to a lower energy state. So once again, it's this sort of dissipation process. There's a physical process of increasing entropy in both cases that brings the electron down to one of the orbitals rather than a superposition of many different orbitals.

2:12:33.8 SC: Same thing is true with a number of particles. If you have a superposition of, if you have a wave function for a field that does not have unique particle number, it will try to settle down either through being observed or shedding energy through radiation or something like that until it is in a state of definite energy, and then it will have a definite particle number. So these are perfectly legitimate questions and tricky ones. They're just ones that I hope I didn't go over too quickly in the book, but certainly they get rarely discussed at all in ordinary quantum field theory courses. Isaac says, "Would you be able to give a quick explanation for what you mean when you say that you are a reality realist? In particular, what differentiates a reality realist from any other sort of realist? For example, if someone believes that mathematical objects are real, could they just say that mathematical objects are a part of reality and call themselves a reality realist? Or would that be wrong?"

2:13:29.3 SC: So you're perfectly fair, Isaac. The label reality realist, which is one that I used as a title of a paper that I wrote, responding to ideas from Justin Clark-Doane, who was a previous Mindscape guest. He's assembling or someone is assembling a collection of papers, responding to his book, Morality and Mathematics. He invited me to be one of the responders. And so I wrote this paper called Reality Realism. It's a bit of a joke. [laughter] My title is a bit of a joke. Sometimes I cannot help myself. I have to have fun, not just be a serious scholar. So the joke is, of course, everyone who's a realist thinks that their version of realism includes nothing but reality, whether it includes moral strictures or mathematical structures as well. My version of realism includes the physical world, and if I was being less jokey and more serious, I would've said physical realism.

2:14:26.0 SC: But that's not as much fun. And I do explain in the paper what I mean by reality realism. So I think that it's not actually misleading anybody, but the idea is that there is some substance to it beyond being a joke. There is some meaningfulness to it because it's not just that I'm differentiating between physical reality and math or morality or whatever, is that there's a good reason to do that. And the reason is sort of the causal closure of the system. And this is not an original notion to me. This is something that people who care about these things have been debating forever. What is the difference between saying that a certain moral intuition represents reality or a certain mathematical structure is physically is real out there in the Plato sphere or whatever, versus saying that it's not? How does the functioning and behavior of the world change?

2:15:25.3 SC: If you think the number two is real, what is the causal impact of the number two on the world? How would the world be different with and without the number two? These are all questions you can answer with respect to things that I think of as real in the physical world. If electrons didn't exist, they would absolutely have a causal impact on the world. I can imagine a world with electrons and imagine a world without electrons, and they're different. I don't know how I can do that with the number two or other mathematical things. So I do think that there is a sensible sense in which the physical world, if I want to call it real, it's real in a different way, and therefore that's what I wanna label as reality. That may or may not be a satisfactory answer, but at least you know, some of my inner thought process there.

2:16:12.6 SC: Okay, I'm gonna group a couple of questions here. Ben P. Stein says, "I'm very interested in hearing a little more of your personal take on Ellen Langer's assertions about mindfulness and its positive health effects from your hard science perspective. Does the methodology and these kinds of studies seem reasonable to you, how much you agree with her conclusions?" And George says, "In your recent podcast with Ellen Langer, she presented some fairly extraordinary claims regarding the benefits of mindfulness. Regardless of the specifics, it certainly seems as though there are some benefits to be had from mindfulness practices. Since there was no reflections for the episode with Langer, I was curious if you had any thoughts regarding the episode and perhaps if you had any personal experience with mindfulness practice that you'd be happy to share." And there were a couple of more questions along the same lines, but they were a little bit redundant, so you get the point of these questions.

2:17:00.9 SC: And I think that, so there were in the comments on Patreon and elsewhere, there were some critical takes on the episode with Ellen Langer, and I think that some of them had a point. There were also some very positive takes, 'cause I do think that in the episode there were some good, insightful things that we learn. But, I think that it's a fair criticism to say that I didn't push back on some of the claims as much as I should have. I think there's a mixture where some of the things she says are very non trivially interesting and good and worth taking seriously. And perhaps she's also overclaiming and putting the fingers on the scales of which evidence should be taken seriously and whether or not it's been replicated and things like that. And, you know, it's my fault because I take it as my job as the podcast interviewer, the podcast are not debates, right?

2:17:57.3 SC: I'm not here to bring people who, who I disagree with and argue with them. I want to get something out of them, something useful, something good. I want them to have their say and then trust to the audience to process that information as they will. So I don't try to spend much of my time as the podcast interviewer taking a negative perspective, but it is also my job to ask tough questions, right? And I think that maybe, it's, will be a legitimate criticism to say that I didn't do that as much in that episode as I could have. After the episode came out, some people pointed out that there have been at least claims that some of Ellen Langer's claims have been overblown. And that's very, very plausible to me. I'm not an expert about that, so I'm glad that people pointed that out.

2:18:48.2 SC: So I'm gonna try going forward to, still have people who say controversial things on the podcast, but, and let them have their say because I don't, I only wanna have people on the podcast who, not necessarily who I agree with, but who have something worthwhile to say. I do think that Ellen Langer has something worthwhile to say, but I also think it's very plausible to critique her by saying that she's overclaiming. And I could have made that more clear as part of my contribution to the interview, as far as do I have mindfulness experiences or practice, I'd be happy to share. No, [laughter] I'm not, I don't, that is not my thing really. I am absolutely open to the possibility that I could have cognitive or happiness level improvements if I did put more effort into that.

2:19:38.7 SC: But where my effort goes is into other things. So I have no special practices to share along those lines, sorry. John Wellborn says, "Are there any benefits of being a scientist that you don't think many people outside of scientists understand? For example, does it help you solve real world problems easier, or does it help you live life with more optimism? I'm just making up those two examples and hoping you can share unique benefits that scientists generally enjoy that non-scientists may not be aware of." You know, I'm gonna disappoint you here, John, and saying, roughly speaking, no, there are no benefits to being a scientist. I mean, I'm sure there are benefits to being a scientist, 'cause to be a scientist, you have to go through training and education, and you have to improve your skills of thinking rationally and deductively. And not to mention quantitatively and empirically and other good things, but I know a lot of scientists and roughly speaking, taking into account that they're all generally smart people who are trained quantitatively, et cetera.

2:20:39.2 SC: Those skills don't really seem to bleed into other sorts of skills as far as I know. You have optimistic scientists, you have pessimistic scientists, you have kind scientists, you have cruel scientists, you have, dispassionately logical scientists, you have emotionally invested scientists, you have social butterfly scientists and introvert scientists. Scientists come in all different forms. So I'm very reluctant to say that there's a set of things that I would overall say, these are benefits you get for being a scientist other than the ability to be a good scientist. Okay, gonna group two questions here. Mark Slight says, "Are the universe inside a black hole kind of ideas worth taking seriously? Is the event horizon in a white hole once we've passed it, can the Big Bang or the CMB be considered a white hole?"

2:21:33.9 SC: And then Gillis 15 says, "Thinking about black holes always breaks my brain. And at some point I always get to thinking about the singularity at the beginning of the universe. Are these singularities actually different? What distinguishes them other than the possibly size? If they are different?" Also, second question, which is illegal. But if it's just a frivolous extra question, sometimes I'll allow it. Gillis says, "What are the best sunsets? Santa Fe, Baltimore, or Pasadena? I'm from New Mexico. I'm partial towards Santa Fe, but I've lived on the West coast, and sunsets on the ocean are great too." Honestly, to ask, answer that last question first, I would rank Santa Fe last in the list of sunsets. I mean, Santa Fe is great for weather and it's gorgeous terrain overall, and the skies are very often clear. So you can see the sunsets and they're very nice. But in some weird way, the dirtiness of the atmosphere in the city gives you more beautiful sunsets.

2:22:28.5 SC: The best sunsets I've seen were definitely in LA because you would have wildfires polluting the air and scattering the light. And even though that's terrible for the environment and the air, it is good for the sunset quality. And likewise, in Baltimore, we've had some sunsets pretty good for similar reasons. Up here in Santa Fe, the air is just too clear. You don't quite get that spectacular color show, but okay, about the universe and black holes, there's a very close similarity between the singularity and a black hole and the singularity, the Big Bang. They're mathematically quite similar to each other. There are two big physical differences. One is that the singularity inside a black hole, as we mentioned earlier, is in the future when you fall into it, the singularity of the Big Bang is in the past. So that might not seem like a very big difference, but it's an important one for your purposes.

2:23:20.3 SC: If you fly into a black hole, you can go visit the singularity, you'll have no choice but to do so. You cannot go visit the singularity of the Big Bang. It's in your past. And the other one, which is very closely related to this, because you know that the difference between past and future comes from entropy, the Big Bang singularity, or it there, again, I should mention there probably aren't any singularities. These are artifacts of general relativity and regime where general relativity is probably not right. So let's take talk of singularity to stand in for talk of right after the singularity, or right before it, the universe was very, very smooth and low entropy near the Big Bang, black holes will likely be very, very lumpy and high entropy near their singularities. But that is empirical feature of what you expect to actually observe in our real universe.

2:24:08.8 SC: It's not a necessary feature of what kinds of things these singularities truly are. Molly Brown says, "While vacuum fluctuations are typically viewed as transient, is there possibility that certain large scale fluctuations do not completely annihilate and could provide a persistent gravitational effect?" So I think that there's a misunderstanding here, and it's our fault as physicists, because the word fluctuations sounds like something happening over time, right? When you think about the bubbles in boiling water, they appear and they evolve and they change. Vacuum fluctuations aren't that, there's no bubbling or roiling in the vacuum of quantum field theory. It's completely static as a function of time. So you really shouldn't use phrases like vacuum fluctuations at all because they evoke this sort of dynamism that isn't really there. I even wrote a paper about this with Kim Body and Jason Pollock about how your thoughts about Boltzmann brains might be different if you took seriously the fact that the quantum vacuum is static, not fluctuating, but there are phenomena that we label as vacuum fluctuations, and actually they come in two very different forms.

2:25:28.4 SC: So the short answer, Molly, to your question, is no, they cannot be dark matter, dark energy, anything like that. They're features that are completely time independent, unlike dark matter, which moves around and collects in galaxies and clusters and galaxies and things like that. But anyway, the two things, the two circumstances under which we talk about vacuum fluctuations. One is when we think about something like a fineman diagram, when we think about particles interacting and tossing virtual particles back and forth, sometimes those virtual particles are referred to as vacuum fluctuations. So in that case, the vacuum fluctuation is not real. It's just a way of talking about the interacting quantum fields in a scattering experiment. The other time we talk about vacuum fluctuations is in something like cosmology where we say the temperature variations in the cosmic microwave background can be attributed to vacuum fluctuations.

2:26:25.7 SC: What we mean by that is there was a vacuum state under the hypothesis of inflation. There was a vacuum state in the early universe that effectively got observed. It got measured by decoherence when the universe reheats when it turns into matter and radiation and things like that. So what was a smooth vacuum state gets measured and it turns into a set of many different branches on each branch of which there are fluctuations, there are slightly different amounts of energy or temperature from place to place. So there, that's an example of a decoherence process and effective measurement of the value of the field bringing in fluctuations into existence. So if you measure something in quantum mechanics, even if the thing you're measuring is static, if you measure it, reset it, measure it again, because quantum mechanics is fundamentally probabilistic, you're gonna get different outcomes, things that look like fluctuations to you. But again, those only happen because you're doing a measurement. So in the paper with Jason and Kim, we even distinguish between dynamical fluctuations and measurement fluctuations. This is something that, again, as I often say, most people don't do, but I think it is an important conceptual distinction there.

2:27:44.2 SC: Sean Connor says, "What are your thoughts on the ages of the current presidential candidates that is Donald Trump and Joe Biden? Is it reasonable to have an age limit for elected officials given an increased likelihood of cognitive decline? Or would that be ageist?" I don't know if it'd be ageist or not, but I don't think it's a good idea. I think that you should let people vote for the people who they want to vote for. And I think that it's perfectly reasonable to ask why people voted for two very old people to be the presidential candidates this year. You know, it's a slightly weird discourse that we're having about the age thing. I do think that both Donald Trump and Joe Biden are very old, and that can possibly lead to cognitive decline. It doesn't necessarily, they're both younger than Jeffrey West who is a Mindscape guest and recent distinguished lecturer at Johns Hopkins at the Natural Philosophy Forum. And I would love to have him as president. He's sharp as attack and totally vibrant, but it can happen and it can happen to anybody. More importantly is what is the system, what is the structure that led to this moment? People voted for these people, Donald Trump in 2016, and Joe Biden in 2020 faced a large diverse field of primary challengers, most of whom were younger than them, and they won. Why is that?

2:29:06.5 SC: And that's a perfectly reasonable question. I'm not saying there's no good answer to it. Part of it is money. Part of it is experience, part of it is strategy, part of it is internal dynamics of the political system. Part of it is the electoral system that gets them there. Part of it is that people preferred them, right? If one part of this has to be, why do people vote for those older candidates? I don't know the answers to these things, but I think that sort of waiting until the procedure has played itself out and given us two very old people and then say, "Oh, I didn't like the result to that. Let's add a new rule in there, or something like that." Is probably not the best way to fix the system. Les Curiata asks a priority question, "While reading through popular physics books, I sometimes come across a statement like, there are no such things as the colors red or green or blue at first sight, this seems like an unreasonable and even provocative claim, but quickly makes sense when backed by the statement that it is our evolved human brains that have assigned colors to particular electromagnetic frequencies to enable us to survive and prosper.

2:30:14.8 SC: If our brains have imparted the notion of colors onto us to help us get buying the universe, then what are your thoughts about our brains also maybe having given us the concepts of space and time to do a similar kind of thing. If this were the case, would that mean that all of our math laws of physics, et cetera, are destined to be constrained within a straitjacket imposed on us by evolution?" Well, on the one hand, sure. [laughter] Many, many features of the world around us are things that our brain chooses to latch onto to give us a better handle on the world.

2:30:48.6 SC: Essentially, all of the emergent phenomena of our everyday world are like that. Not just objects like tables and chairs, but processes like classical mechanics, right? We know that quantum mechanics is more fundamental than classical mechanics. In my favorite view of quantum mechanics, things like particle positions and velocities do not exist. They're not part of the fundamental ontology, but they're super useful to imagine that they exist in apprehending the immediate world around us. Maybe space and time are similar, so sure, I'm happy to believe something like that on the one hand, on the other hand, rather, does that mean that we are destined to be constrained by our experience and evolution and things like that to sort of not get it right, to not see deeply into the fundamental nature of reality? No, I don't see any evidence for that whatsoever. After all, when it comes to the colors, we have come to understand the electromagnetic spectrum when it comes to classical mechanics. We have come to understand quantum mechanics.

2:31:53.6 SC: It's called science. Science helps us look beyond the limitations that are provided to us by evolution and other things, and we can find better descriptions underlying them. I see no reason for that to stop. Robert Rux and Rescue says, "Suppose you love someone very much, but she doesn't love you back. You pray to God that she reciprocates and surprisingly God appears and offers you to change her brain structure in such a way that she actually does love you back. Would agreeing to this be less legitimate than if she naturally loved you just by the chance of the initial conditions at the Big Bang?" Well, I don't know about the naturalness or legitimacy, I'm not quite sure what valence we're putting on these judgmental words, but I would not take the bargain that God offered in that particular case.

2:32:39.9 SC: And I think that it's actually the reason why I chose this question to answer is I think it's a important lesson here. Most people in the course of their romantic histories have been more in love with someone than they've been in love with them. Maybe completely unreciprocated, or maybe it's just a little bit more strongly felt on one side or the other. That's the nature of the activity, and it's very tempting to imagine like, if only I could flip a switch in this person's brain so they would love me just as much. The problem is that there's no switch in the brain that says, love this person or not. The brain is a complicated, interconnected network of things going on. It's impossible to imagine just changing that one feature of the person. Maybe the reason why they don't love you is based in something legitimate and real.

2:33:30.2 SC: Maybe they're not the right person for you, right? So I think that it's not just that it would feel like cheating to have God do that. I think that it's not the right way to think about people, and more often than not, when someone doesn't feel the same way about you, that you feel about them, the right thing to do is to move on and find someone who does feel the same way about you. Eric Copenhaver says, "Priority question. I always wanted to pursue what is good. When I started grad school, I tried to derive that from some ethical axioms so I could direct my choice of what lab to work in. Eventually, I ended up in Adam Interferometry, but it led to some existential struggle as I failed to really get into a satisfying answer. How do you think about goodness and how to pursue it?"

2:34:18.1 SC: I like the idea that maximizing the good of the world leads you to become an Adam interferometer expert. But maybe it does. Maybe there's something there. How do I think about goodness and how to pursue it? I tend to think that it's hard to quantify it. I think that trying to find an equation for it might be too difficult. Well, more than too difficult might be the wrong question to kind of ask to derive things from ethical axioms. I absolutely sympathize with the impulse, with the feeling that that's what we should do. I too, when I was starting grad school age, that is to say undergraduate age, thought about ethical axioms and how to derive correct behavior from them. In some sense, that doesn't seem to be asking too much, right? If we think that there are answers to the questions, what is a good act and what is a bad act, then it is almost inevitably true that there should be some axioms from which we can derive what those answers are.

2:35:25.2 SC: But if, I'm tempted to think these days that there just aren't answers to those questions in the most common construal of what the word answer means, that is to say sort of an objectively right answer that could be agreed upon by different people under all circumstances, and even by one person under different moments of their lives or something like that. I think that we need to reconceptualize good and moral and right in terms of something more moment to moment, something more contingent, something more judgmental and subjective. As I've said before, I don't have a fully blown theory of this. I wish I did. I would like to, but the theory might not take the form of a set of axioms from which you derive cut and dried results to tell you what is good, in the meantime. Mostly, you know it when you see it.

2:36:21.7 SC: Mostly you try to be generous and kind and open-minded and helpful rather than selfish and cruel and closed-minded and unhelpful. Those are the things that I would try to be. Florian Bozel says, "Sabina Hausen Felder recently mentioned John Moffat's theory, MOG, I think, I think MOG stands for modification of gravity or something equally uninspiring in terms of the acronym. As an alternative to GR that might be able to explain dark matter, are you familiar with Moffat's theory? If so, what is your opinion of MOG?" I'm not very familiar with the current version of Moffat's theory. Moffat has had a theory for decades now, and the theory keeps changing, and I am pretty much, well, I would put a lot of money on the idea that it's not well-defined because these theories are harder to make up than you might imagine.

2:37:20.6 SC: When you just start pushing around equations of motion for gravitational fields of various sorts, you generally run into problems like the energy is unbounded below and the vacuum is unstable and things like that. And I'm not at all, I'm pretty sure that there's, that has not been checked for this particular kind of theory, but, so I'm not, and I'm not really that optimistic that you need to, that you can replace dark matter with modified gravity. So I'm not paying any attention to this. I'm not putting any effort into it, but I'm answering the question because I have a fun personal anecdote about Moffat's theory of gravity, when I was an undergraduate. So this is the 1980s, remember 40 years ago, we can admit it. I was an undergraduate of Villanova in the astronomy department, and two of my professors there, Ed Guyon and Frank Maloney, who are very good astronomers, they were doing measurements of variable stars, binary stars in this case as tests of general relativity.

2:38:18.2 SC: And they did a very comprehensive analysis of one star system, in particular DI-Hercules, which is a binary star, which has procession of its orbit. So this an elliptical orbit for this binary star. And it processes just like mercury processes, and you can make predictions for how much procession you should get, and you can, general relativity turns out to be an important part of it. Part of the procession just comes from the fact that the stars have spin and they have internal structure and things like that. So most of the effect just comes from Newtonian gravity. But there is a GR effect because the stars are massive and the period is small and they're close together, et cetera. The eccentricity is high. So you can try to use this as a test of general relativity. And general relativity fails if you take the data at face value.

2:39:09.4 SC: So if you just plug in the predictions and you compare them to the data, you get the wrong answer for the procession of this variable star. And there's a couple other stars. V541 Cygni is one that I worked on where there's a little bit of a hint of that problem also. So knowing what I know now, what I would've said is, Look, changing general relativity is very hard. We have a lot of evidence, in fact, we have a lot better evidence now than we did back in the 1980s for the correctness of general relativity, from binary pulsars, gravitational waves, LIGO type things, many other things. So it's even harder now, but even then, general relativity is hard to modify. Whereas stars are messy and hard to understand the internal structure, are they tilted? What, you know, is there extra gas or are there third bodies in the system?

2:40:00.0 SC: There's a million down to earth explanations that you could imagine. And Ed Guy and Frank Maloney tried their best to go through the different possible explanations, and they gave reasons why they didn't think that they worked. But still there's room there. And so the right thing to say is, look, keep studying this. Look for other examples, but don't throw away general relativity. At least not right away. And one of the things that was, so John Moffat knew about this anomaly, and he had his theory of gravity, which at the time was called NGT, Non-Symmetric Gravitation Theory. It was a version of a torsion theory, if you're familiar with those. And he claimed that he could fit the data. But again, I was very enthusiastic about this at the time I was an undergrad.

2:40:47.7 SC: You're like, "Yes, we're gonna overthrow general relativity. Huge important thing for science." So I was very pro Moffat's theory of gravity. As I came to understand better and better what was going on, I realized that Moffat's theory had a lot of free parameters. He felt free at some point to imagine there was a whole bunch of dark matter inside the stars that was pushing around the stars in weird ways because of his theory of gravity. And it was, every sign of sloppy science, let's put it that way, waiting until the day to come in and then adjusting your theory to say, "Oh, yes, that's exactly what I predicted all along." For many reasons, dark matter exists. Okay? I will say, I've said it before I said it again. If someone says they have a new theory of gravity that gets rid of dark matter, ask them to show you their plot of the temperature anti isotropy spectrum for the cosmic microwave background.

2:41:47.1 SC: That's the best evidence we have for dark matter. If they can't do that, they haven't explained away the dark matter, you don't need to pay attention to them. Ilya Levak says, "In a recent a MA episode, you read a couple of favorite poems. I'm not a native English speaker, but I've lived in the UK for greater than 10 years, have written a PhD thesis in English. I'm working here now, generally have no problem communicating in English, but these poems sounded like gibberish to me." [laughter] Is it gibberish or gibberish? Gibberish. I guess. I'm a native English speaker. I don't even know these things. "Moreover, any other English poems I encounter also do." So I'm glad you mentioned that, Ilya. "So it's not just my readings that were the problem there. So the question is, has poetry always made sense to you as a native speaker, or is comprehending poetry a special skill you've developed over the years? Are there any entry-level poems that helped you start understanding and appreciating poetry earlier on?"

2:42:42.0 SC: Well, so I would ask very quickly, Ilya, for you, have you read poems in your native language and do you find them easier to understand? I don't think that good poems are necessarily ever easy to understand. The idea of a poem is to take the language that we speak in and really like distill it down to an incredibly compact, densely packed set of images and meanings and similes and metaphors, right? It is necessarily a different thing than the kind of floppy, redundant writing style or speaking style we have in ordinary prose. A poem is kind of like freeze dried prose, right? You've boiled out everything that is unnecessary and you're left with something that is very, very dense. So it should be no surprise at all that faced with a poem in whatever language, native or otherwise. It takes effort to read it and understand what is going on. Oftentimes there are hidden meanings below the surface. There is sort of a surface description and there's a metaphorical lower layer or more.

2:43:53.1 SC: And it is absolutely a skill to be able to do that. I don't have a very highly developed ability to do that. I have a little bit, 'cause I think the poetry is good, and I enjoy reading it, but people who are really experts are way better at it than I am. And guess what? You have to work to develop that skill, whether it's reading poems or thinking about, reading books about how to read poems. That is something that is absolutely, something you can do. So I wouldn't despair that it's impossible. I would acknowledge that this is a skill that if you want to, you can set out to learn and become better at. Dom asks a priority question, "You stated that you don't see any reason to change your lifestyle for climate change related reasons because nothing you will do will have any appreciable impact. You also encourage people to vote and presumably vote yourself despite it also having no impact. In fact, there are changes you could make to your lifestyle that would have a tiny but non-zero impact on climate, e.g. Drive less, whereas your vote will have literally no impact at all.

2:44:51.1 SC: I'm curious about how you resolve the seeming contradiction." So, I don't think I've ever said that there's no reason to change your lifestyle for climate change-related reason because nothing you do will have any appreciable impact. It's possible that I've said that. As I said before, when you talk enough and you talk on AMAs for hours and other places, sometimes you say things that are not precisely aligned with the meaning you're trying to get across. What I will defend, what I do try to say, is that, the way to approach problems of climate change and things like that is not through individual people changing their behaviors, because that's not the way to do it. That's not going to be effective. That's not going to be the kind of solution that actually gets the problem solved. In those situations, you need systemic change. You need to think about laws and international agreements and changing the incentive structure so that people do exactly what they want to do, subject to the constraints of the incentive structure, and that thing that they want to do ends up saving the climate, okay? That is why this is not a good analogy with voting. But I should also say, there's nothing wrong with doing things personally that you think make the world an infinitesimally better place.

2:46:12.5 SC: That's great if you wanna to do it. It might, you can either justify it because even a little bit better is still better. Even if it's a little bit, it still counts. And you can also justify it that it makes you feel better, that it makes you feel like personally you are trying your best to make the planet a better place. Those kinds of justifications are 100% legitimate for doing individual actions to fight climate change or whatever. My only point would be they're not actually going to be the ways that the climate is protected. Whereas with voting, it's a very different circumstance. The only way that we get a result through voting is through the individual actions of the voters. Now, you may say that it is unlikely that any one person's vote is the deciding vote. In fact, we had this conversation with Herb Gintis on the podcast not too long ago, and I would get that that is a valid argument, but there is no alternative to voting. Literally, the outcome is the combined collective result of many people going to the polls and voting. So the only thing to do is to vote. And I think that voting is important for exactly that reason. So, I want to make the world a better place. My thoughts are engaged in what is the way to effectively make this happen.

2:47:32.4 SC: In terms of electing politicians, it is getting out and voting. In terms of the climate, it is enacting systemic changes so that people don't want to do things that destroy the climate. Nanu says "I always ty to steer clear of questions outside of physics arena, however I can't help but ask you how do you feel about what is going on in the country right now? Are you worried that the direction we're headed to? How do you keep your cool? I'm an immigrant who ran away from places of oppression to start all over and give my children a better opportunity than I did, justifying the glimpses of what I dreaded the most back there finding it's way here as well. It's hard to ignore what's going on anymore." Yeah, I'm very sympathetic. Look, I try to keep a brave face. And as I said at the intro to this podcast, I think it is crucially important to keep fighting and try to make the world a better place. But the augurs are not very encouraging about the state of our democracy and our world right now.

2:48:36.6 SC: It's not just that there are political figures who do not believe in democracy and are authoritarian in their impulses. It's that people support them, right? That's the problem. And not only vast unwashed masses support them. That happens and it's true. But whole bunches of what you thought were the responsible elites in power structures support them also. And it's not just in the United States. It's in other countries as well. And that's very depressing. Democracy isn't, and it's not just democracy. I use democracy sort of as a shorthand for living in a society with respect for individual rights and mutual tolerance of different viewpoints. And then very, there's a whole bundle of things that go along, values that go along with this attitude towards living in the society. And there's a whole bunch of people out there in power and not in power who are not that invested in that. They would be happy. Look, the Supreme Court decision we talked about is one example, but there's much stronger versions of that by certain politicians, et cetera. That basically make it clear that they consider it to be a game and the goal is to win the game. The goal is not to fight fair and see what happens.

2:50:01.8 SC: Rishi Sunak, who is the Prime Minister of the UK, who recently lost his election, even though he's a conservative, he had a little dig when he gave his concession speech. He was like, "Of course we accept the outcome of this election and we'll peaceably transfer power," because some people are just not into that. Anyway, so there's plenty of reason to be anxious to be worried about the state of the country. And that's all the more reason to keep fighting, to try to, fighting in the broadest sense in some very, very tiny way. Having a podcast and trying to get people energized to fight for democracy is a little bit of a fight. We were having this discussion on Blue Sky the other day. Like some people were saying like, ah, I'm here, on the Internet and social media arguing to try to make the world a better place. But it has no impact.

2:51:00.0 SC: What is the point? And others pointed out correctly, look most things you can do will be small in their impact, but not zero. You still got to do them anyway. Not everything you do has to be of revolutionary importance. It might come to a point where we need to contemplate acting more strongly. Like right now, I can still mostly live my life as a scientist and philosopher, writing books, doing podcasts and whatever, doing my research, teaching my classes. If I really thought that literally democracy was collapsing in the United States, I might very well reorient my energies to try to prevent that from happening in a much more dramatic way.

2:51:39.7 SC: Maybe I should already. I don't know. Maybe I'm making the wrong choice by still doing podcasts and writing physics papers. But, you have to, it is going there. What can I say? Most people in the United States of America do want there to be a democracy, but there's their individual people have conflicting opinions that might not necessarily be coherent. So they might be willing to do anti-democratic things for the sake of other goals, like the support of this particular politician or the enactment of this particular policy or things like that. And I do think that there's still plenty of room to convince people of the importance of the value of democracy in and of itself, regardless of what outcome the democratic elections get you. The fact that you do it through the course of democracy is intrinsically important. I think that we don't do a very good job of that. And I think that value exists, but is relatively weak in a lot of people, including a lot of liberal minded people. It's not just a conservative thing. There's a lot of people who think it would be better if we had a single strong leader to just impose correctness on the world.

2:52:57.9 SC: And it's a very non-democratic way of thinking. And I don't think, I think we've taken democracy for granted for too long. We don't do enough to make the positive case that even if democracy doesn't always get the right answer, it is still much better than putting power in the hands of one or a small number of people and letting them do what they think is right. There's an intrinsic value to locating both power and authority in the broad scope of people who are citizens of the country. We need to make that case better than we have. Anyway, Johan Lofgren says, "From your interview with Cumrun Vafa, I understood his position to be that following Effective Field theory principles is not enough when gravity is involved. Does that mean that the Wilsonian view is doomed to fail at some point?" Well, there's two things. One is it's not that Effective Field theory principles fail in what Vafa is talking about, because what he's saying is you can do Effective Field theory. And the problem is that is compatible with too many Effective Field theories. We think there is one correct theory of the world. And you do Effective Field theory on that and you get a low energy theory that is hopefully the standard model of particle physics plus whatever. And that's great. And Vafa's point is that if all you think about is the low energy Effective Field theory, you're gonna be able to study other theories besides the standard model of particle physics.

2:54:25.4 SC: You're gonna have a lot of other possibilities that don't connect to some good theory in the ultraviolet, a good theory that includes gravity, whether it's string theory or whatever. So it's not that Effective Field theory doesn't work, it's that it's not enough to pinpoint what theories are physically legitimate, right? Now, having said that, it might still be true that the Effective Field theory philosophy a la Wilson will ultimately fail. Maybe quantum gravity is a different kind of thing, right? Effective Field theories are still field theories, and there's good evidence that quantum gravity is not a field theory at some fundamental level. It acts field theory-like at low energies, long distances, etcetera but probably not in short-distance or high-energy physics. So we have to be open to something very, very new happening. Robert Grenice says, "I am rereading The Big Picture, one of my favorite books. I believe that I understand the arrow of time as we move from low entropy to higher entropy, and it makes sense that things become more complex at a fundamental level. You say this also explains why we age, which I don't get, as aging is a biological process. Or do you simply mean we age in the sense that time passes, so we are older in the same way the earth gets older?"

2:55:41.4 SC: No, I mean aging in the sense that, like, my back hurts more and I recover from injuries more slowly than I used to. I mean what we mean by aging. Aging has an arrow of time, and I would claim just on very broad principles that almost everything in the universe that has an arrow of time has an arrow of time because of the increasing entropy of the universe, a la the second law of thermodynamics. Now aging, or anything else in biology, has to be compatible with the laws of physics, including the second law of thermodynamics. So that is included in the set of things that pick out a direction of time. But the connection between the fundamental arrow as defined by entropy and the emergent phenomenon of aging or other biological processes might be very, very difficult to work out. So if you wanted to ask me, to explain to me why I recover from bruises and sprained ankles more slowly now than I did when I was young using nothing but the second law of thermodynamics, that would be difficult to do. I think it's possible in principle to do it, but doing it is actually work. There's many layers of emergence between the laws of physics and my ankle. So I'm not gonna tell you there's a simple connection there that I can sketch out in a few sentences, but I do think that it is there. Josh Charles says, "I really enjoyed the recent-ish episode about the Margaret Mead book. Her contributions to cybernetics were mentioned but not really explored.

2:57:14.0 SC: Recently, I've been exploring this field, and it sounds like it's got a lot to say about topics covered in this podcast, causality, information, chaos. What is your view of cybernetics as a field, in your opinion? And in your opinion, is it worth diving into? Could we get some more podcast episodes regarding this perspective?" Well, it's interesting because I was just reading a paper by David Krakauer, a recent podcast guest and President of the Santa Fe Institute, where SFI has put out a four-volume set of classic papers in complexity theory. It's super good, it's super valuable. I'm very glad they're doing this at a relatively affordable price point. Still not super affordable, but you know how it is with academic books.

2:58:01.2 SC: But so David wrote this expansive introduction where he goes through the history of complexity and he puts different things in context and it's 100 pages, just this introduction. And it's super duper useful for someone like me who loves complexity but has not grown up thinking about it. And one of the points he makes is that cybernetics is sort of proto-complexity as a discipline, right? That cybernetics was an example of bringing together ideas from computer science and control theory and engineering and statistical mechanics and physics into trying to synthesize them into something. And so his answer, I think, would be that cybernetics was a good step along the way to what these days we would call complex systems analysis or just complexity theory.

2:58:53.1 SC: I'm not in a position to tell you whether that's right or not, but that sounds roughly right, to me. So rather than studying cybernetics for its own sake, I think that the right thing to do these days is to study complexity more broadly. Speaking of which, Laura says, "Your mention of being in Santa Fe reminded me to ask you to let Mindscape listeners know that the Santa Fe Institute has a lot of great free online courses and tutorials. Anyone who wants to know more about the fundamentals of complexity science should check out complexityexplorer.org. Topics range from introductions to complexity and information theory, to relevant mathematics, basic differential equations, vectors, etcetera, to coding for complexity models, to complexity in biology and social sciences, and I would also add Origin of Life is a course that they have. After taking several of the courses, I understand the vocabulary and references of experts talking about the field.

2:59:44.3 SC: It's highly recommended." So there's no question there, which is fine, because I'm just gonna endorse everything Laura said. If you didn't already know, if you are intrigued by this complexity stuff, go to santafe.edu, which is the SFI website, and look for Complexity Explorer. Or just type in Complexity Explorer to your favorite search engine and you will find it. Or just go to complexityexplorer.org. They have many tutorials. They're free. You can either join up, sort of to take classes simultaneously with other students, or you can just watch lectures and things like that. It is a great way to learn about this vast and interdisciplinary field.

3:00:23.9 SC: Roland Weber says, 'Your poll among Patreon supporters regarding the preferred format turned out in favor of audio only episodes plus reflections rather than video episodes. What is your personal preference on this question and why?" So yeah, for those of you who are listening to this who are not Patreon supporters, on Patreon, after every episode, I put up a short, five or so minute reflection where it's just me talking about what sort of popped into my mind as a result of doing this podcast episode. So it's a little bit of, my take on what just happened. And I've been doing this for, I don't know, a year. It's an extra little benefit for Patreon supporters. But I have been toying, I'm always toying with the idea like how to, on the one hand, improve the podcast and make it better without, on the other hand, doing any extra work. So what I experimented with for a couple months is doing video versions of the podcast. You wanna record the podcast, even though they're all virtual, I can just click record on whatever thing that I have on my screen and get a video of me talking to the person. Okay. It's harder to do that than just the video for various reasons. Number one, editing it is harder. It's both slower and clunkier. Number two, it is harder to adjust the audio quality on the video file.

3:01:43.9 SC: It's possible, but harder to do that. Number three, both you and the guest are knowledgeable, are aware, cognizant of the fact that you're being recorded, which is a little bit more effort in the moment when you're actually talking back and forth to each other. So I did this for just as an experiment. And then we asked people who are Patreon supporters, which I basically said, look. It's more work to do the video versions of the podcast than it is just audio. So what we'll try is I will not do the reflection videos. I'll just do the video for the podcast itself and see how that goes, see whether that's more value added. And we did that for a while and did a poll. And overwhelmingly, the answer was people liked the reflection videos rather than the videos of the full podcast. So we stopped doing, just recently, we're in the transitional period right now where there's still a few video versions yet to go, but mostly as reflections, I believe.

3:02:45.9 SC: That's right, I forget. Anyway, so the question is, what do I prefer? And the answer is, I have realized through doing this experiment, you have to do the experiment to realize it. I don't like the video thing at all. It's way too much work. But even more than that, it's just like the little bit of extra effort being expended while you're on the podcast. And then when you have to edit it, that is just really, it's one more thing that has to be overcome. And I've said it many times, I know you're tired of hearing it, but I have to limit the amount of effort I put into the podcast. If I were doing the podcast full time, if the podcast were my job, I would do videos and I would release them to everyone, not just Patreon supporters.

3:03:26.2 SC: And I would put much more effort into growing the podcast. The actual audience for the podcast has been static for years now. It's well known, the podcasting community, that podcasts don't go viral, right? There's not sort of a discovery mechanism 'cause most people are not sitting at their computer listening to the podcast. They're in the car or they're walking around, it's on their phone or whatever. It's hard to click on the next podcast or something like that. So I don't know how to grow the audience for Mindscape, and it certainly hasn't been growing. But if I were full time, I would try to do that much harder than I am, and maybe video be a component of that. As it is, with my one-day-a-week effort at podcasting, I'm more or less content with how things are. Audio only is the way it's gonna be. The audience is gonna be whatever the audience is going to be. Leaving reviews on iTunes, etcetera helps for that little tiny bit. I appreciate it when people do that, but mostly I think the status quo is gonna remain the status quo. Final question. Eduard Sackinger says, "Vectors are usually explained as something that has a length and a direction like an arrow.

3:04:38.0 SC: In contrast, tensors are usually described, not very helpfully, as something that transforms like a tensor. Can you give a better geometric explanation of what a tensor is? It seems to me that a rank two tensor encodes two geometric objects, one for the symmetric and one for the anti-symmetric part, but I'm unclear how to interpret the latter." Okay, I put this last. This is the last question of this AMA, and I put it last because I'm very tempted to ramble on for a while about this in a way that I suspect will be completely unhelpful, but you did ask for it, Edward. Because it's actually a very deep, interesting question for those of you who are mathematically inclined out there, by which I don't mean mathematically expert, but sort of mathematically interested. This is a great, this question of what is a tensor really? Is it really more geometric or something else? Is there a geometric way of thinking about it? Is a deep one. And the reason, there's a couple of reasons. One reason is that the way that tensors appear to us in applications are generally in the form of tensor fields, okay? So what I mean by that is if you have general relativity, for example, and you say spacetime is curved, and I code the information about the geometry of spacetime in a metric tensor field, that means that at every point in spacetime, there is a metric tensor, okay?

3:06:03.8 SC: There is a set of components, if you want to express it that way, g, mu, nu the metric tensor components in some coordinate system, or you can do it in coordinate-free ways, that's fine. But the point is that there's the idea of the tensor and the idea of the field stretching throughout space, and these are different things. You could just have a tensor by itself at one point in space and ignore the fact that there are other points in space and think inherently, intrinsically about what a tensor is for its own sake. And my point is just that we tend to skip over that step a little bit. You know, there are... There is, as we said before, talking about how physicists dream. There are sort of equation-oriented physicists and picture-oriented physicists. Same thing is true for mathematicians. The rough division is into algebraically-oriented mathematicians and geometrically-oriented mathematicians. And of course, any good mathematician is both. But it's very very true that different people have different styles and so this whole general relativity geometry of space-time field tensor field etcetera that lives in the realm of geometry but tensors by themselves kind of live in the world of algebra, of of linear algebra in particular and so now I'm getting to the answer to the question Linear algebra is the study of vectors and generalizations and constructions you can make from vectors.

3:07:36.7 SC: So a vector, what is a vector? Well if you want an unhelpful definition, a vector is an element of a vector space. And well what does that mean? It doesn't mean an arrow with a direction and a magnitude. We think about it that way and it's perfectly a valid way to think about it. But if you get really mathy, a vector space is a set. Okay, so you have a set of elements with a couple of operations defined on that set. One operation is addition, so you can add vectors together, and the other operation is scaling. You can multiply by numbers. If it's a real value vector space, you multiply by real vectors. It's a complex value vector space like Hilbert space, you multiply by complex numbers, etcetera. So that's what a vector really is. Vectors are things that you can add and scale by numbers. Let's say real numbers because let's think about real vector spaces okay? It turns out that once you get that definition, you can represent vectors as little things that with arrows, right? Because you can imagine the space, the whole vector space, you could set up some basis vectors, and then you can draw your little vector as a set of components that add together to make the arrow that you're thinking about.

3:08:51.6 SC: Okay, so that's a space by itself, the space of vectors by itself. Now, if you were doing general relativity, etcetera, you would say, well, what are these vectors? And you would have a whole set of geometric answers to that. You could get very technical and talk about equivalence classes of derivatives along parameterized curves through a point. Let's not get that abstract, okay? So I'm just letting you know, 'cause there are some experts out there listening. I'm not thinking specifically about the tangent vectors to a manifold or anything like that I'm just thinking about the abstract notion of a vector space and of course if you're a mathematician and you're given this vector space you start asking what can I do to it. What operations can I perform on it?

3:09:35.6 SC: And one thing you can do with a vector space is you can imagine ways of assigning numbers to each vector. That is to say, you can have a function on the vector space, right? To each vector, you give a number. Just like for the real line, which is, by the way, a vector space, I can have functions on the real line. You know, f of x equals x squared or whatever. But this feature of vectors that you can add them and scale by real numbers this makes vectors naturally live in the world of linear algebra right algebra is the is the field of multiplying and adding things together that's what algebra is as opposed to calculus where you take derivatives or anything as we discussed in an earlier AMA question the quadratic formula ax squared plus bx plus C equals zero that's algebra that is quintessentially algebra because you've multiplied X by itself to get x squared, then you multiplied it by a and b, and you've added them together, etcetera.

3:10:34.1 SC: Algebra, symbolic manipulation of multiplying and adding things together. Linear algebra is when you restrict yourself to not including X squared. So this is the quadratic formula. Quadratic equation is x squared, ax squared plus bx plus c equals zero. Linear algebra deals with only linear transformations. So I'm allowed to take x and scale it by multiplying it, so bx, and I'm allowed to add to it. That's also a linear transformation. So bx plus c that's part of linear algebra if I add ax squared that would be quadratic algebra or something that's not included so linear transformations are things that are why add them together scale by numbers and that's naturally associated with vectors vectors naturally live in the world of linear algebra so instead of just asking what functions I can put on the vector space let me ask what linear functions I can put on the vector space what does that mean? That means if I have two vectors, v and w, and I have some function of these vectors, so I have a function f of v, that I can also ask what is f of w, but I want this function to have a special property. I want it to be linear, which means that if I take f of v plus f of w, I want that to equal f of v plus w. So, in other words, I can add the vectors together and then apply the function, or I can apply the function to two separate vectors and then add them together.

3:12:10.6 SC: That's what would be a linear function. And there's not that many ways to do it. If I take the vector and I square it, whatever that would mean, that would not be a linear function. There are very, very few ways to have linear functions on vector spaces. In fact, the number of linear functions, you can parameterize all of them. And the set of linear functions on the vector space is itself a vector space. This is something, if you're truly mathematically inclined, you just got a warm and fuzzy feeling when I said that. This is what makes mathematicians all happy and inspired and feeling good about the world when you say things like the set of linear functions on a vector space is itself a vector space. That is to say. I can take two different functions, f and g, of my vectors, and I can add them together, and I can scale them by numbers. So the set of linear functions on a vector space is a vector space, and indeed, it is a vector space with the same dimensionality as the original vector space.

3:13:12.1 SC: Okay so we call it we give it a special name it's called the dual vector space the dual vector space is the space of things space of linear functions on the original vector space it's a vector space itself and if you say okay what is the dual of the dual vector space it's the original vector space so you have two vector spaces same dimensionality they're different they're not the same space but they're the same dimensionality and you have a map that goes from one to the other and vice versa. For each vector space, you have the space of linear functions on it, and that is dual to it. Okay, why am I telling you this?

3:13:48.4 SC: The question was about tensors, right? Tensors are just a generalization of this idea. That's the real abstract, super powerful definition of what a tensor is. I start with some vector space. That's always the starting point. I construct the dual vector space. And then I consider collections of vectors and dual vectors. So let's say I have one vector and one dual vector. That's a collection. Or more abstractly, I have one copy of the original vector space and one copy of the dual vector space. Okay. What am I gonna do with that? That's a new space. If the original vector space had dimension d, Then the dual space has dimension d, and the combination, original vector space and dual vector space, has dimension d plus d, so 2 times d, okay? Guess what? That combination, vector space plus dual vector space, that is a vector space. All the elements of that I can add together, and I can scale by numbers. You see where this is going. That's a vector space, and I can say, well, let me think about the space of linear functions on that vector space. So to keep track so we don't get lost here, we have vectors. We have linear functions on them, which are dual vectors. So we can combine them together in any number you want. Here's several vectors, several dual vectors. I'm gonna smoosh them together. The space of all that ordered, not ordered pairs, but ordered sequences of vectors and dual vectors.

3:15:25.0 SC: And I can ask, what is the space of linear functions on all of those the answer is a tensor that's what tensors are that's the real algebraic hardcore definition of what a tensor is a tensor is a linear map a linear function from some collection of vectors and dual vectors to the real numbers so let's see this in action what is the tensor that we know and love the metric g, mu, nu right in practice it looks like a little matrix 4 by 4 matrix in space time but you could do a metric on three-dimensional space or n-dimensional space or whatever be an n by n matrix and that has two lower indices when you write it in tensor notation vectors by this way of thinking which you'll read about if you read my general relativity textbook etcetera, vectors have upper indices, so the metric tensor with two lower indices is a map from the vector space plus itself to the real numbers. What does that mean? It means they give me two different vectors and I now have a function, a linear function on these two vectors.

3:16:38.5 SC: What is that function? And the answer is their dot product or their inner product, if you wanna think of it that way, v.w. That's what the metric tells you that's what the metric lets you do a function is an assignment of a number to some space in this case the space is two copies of the vector space the vector space is whatever you want it to be the metric on that vector space assigns a real number to any pair of vectors which in this case is interpreted as the dot product v.w and then you can have the Riemann tensor has one upper index and one lower index that means it is a linear map from a space, the product of one dual vector and three regular vectors to the real numbers. And if you read, again, my general relativity book, it'll even tell you what those vectors and dual vectors are.

3:17:29.3 SC: It's a very specific map, a very specific set of vectors and dual vectors to the real numbers. Okay. So you asked for it, Edward. Sorry about that. Is that a geometric explanation no not really it is an algebraic explanation but it is the right explanation and then you need to think about how to interpret that geometrically so I didn't do much of this in my general relativity textbook, but famously or infamously, if you read Misner, Thorne and Wheeler, the big phone book, general relativity book, Kip Thorne, of course, former Mindscape guest, they bent over backwards to give geometric interpretations to various kinds of tensors. It's super hard and not especially satisfying.

3:18:17.7 SC: This is why, depending on how into this kind of thing you are, you either love or hate that book. But here's the kind of thing that they say. Think of a vector, think of a vector geometrically. So think of it as an arrow with a direction and a magnitude okay? What the dual vector is, is a map from vectors like that to the real numbers. What does that mean, a linear map? Well, you can think of it as rather than a line segment, like a little arrow, the dual vector is almost like a plane that stretches flat all throughout the vector space but it's repeated so a bunch of parallel planes a fixed distance apart okay so basically like a division of the vector space by parallel lines or planes or whatever and if you have every such thing every such way of dividing the vector space with parallel planes gives you a dual vector and that means if you give me a vector I can calculate a number from it.

3:19:22.3 SC: And the number is the number of times the little arrow intersects the plane. So if you think all of these planes are equal distance from each other and perfectly parallel to each other. And I draw a little vector. If the vector is completely parallel to the plane, it only intersects at zero times. It just stays parallel to it, and therefore the function gives you zero. Whereas if the vector stretches transverse perpendicular to the plane rather than parallel to it it will hit it many times and that number of times it hits it is the number that the dual vector is returning and they say it's like the bongs of a bell thinking about how many times you follow the vector through the planes it will go bong bong bong bong every time the vector hits these parallel planes you got to read it. And I mean it's literally that's the point in that general relativity book where some people fall in love forever some people toss the book out and never read it again. So you wanted to know and look there's no rule that says that everything in math or physics has to have a simple intuitive explanation.

3:20:29.8 SC: Okay. I thought that maybe it would be worth in this case, giving you the right explanation, the closest thing to an accurate, rigorous explanation for what a tensor is. That's what it is. It may or may not be easy to visualize that or to intuit it. That depends on how you like to personally conceptualize these things. You can go very far just pushing around the symbols, right? Most physicists don't worry about these bongs of a bells or pictorial representations of dual vectors, much less higher order tensors. They just know how to push around the equations. Is that all you ever wanna do? Push around the equations? No, you would like more than that. You would like a deeper understanding, so it's good to ask. But I never promised you a rose garden. Sometimes when it comes to math or the physical world, we have to take what we can get. On that note, thanks for sitting with me through this long AMA. Thanks for supporting Mindscape. I deeply appreciate it. Take care.